Skill Interaction Framework
GM’s Workbook — Design Reference
Every skill check in this campaign is designed according to the principles below. Read this once before Session 1. Return to it when a player tries something unexpected and you need to know how to handle it without improvising against the grain of the system.
The Seven Principles
1. No Dead Ends
Every failed check opens a different door, not a wall. “Nothing happens” is the worst possible outcome of a skill check: it removes player agency, wastes table time, and teaches players that trying things is unrewarding.
In practice: When a player fails a Persuasion check with Quartus, they do not get nothing. They get the official process: slower, auditable, and now visible to Corvinus. That is a consequence, not a wall. The information is still accessible; it just costs something different to reach.
Write failure states before you write success states. If you cannot describe what failure opens, the check should not exist.
2. Wrong Tool, Different Door
The wrong skill does not fail: it succeeds into a different situation. Intimidating Valeria does not terrify her; it makes her clinical to the point of being useless, treating the party like difficult patients rather than colleagues. They got something, just not what they wanted.
In practice: Every significant social interaction should have at least two skill approaches mapped. Persuasion gets one result. Insight gets a different result (understanding the NPC’s real position rather than changing it). Deception gets a third (short-term compliance, long-term wariness). All three are successes. The quality of the success differs.
Document these per NPC in the relevant chapters.
3. Cascade Design
Succeeding at an early check reveals the existence of a harder, more rewarding check. Players who invest in a relationship should discover new things to unlock, not just the same things more easily.
In practice: Reaching Ally tier with Rufus does not give you a better blacksmith. It gives you a different resource entirely: his Germanic knowledge, which opens a separate DC 14 History check that identifies the metalwork he describes. Each tier reveals that the next tier exists and is worth reaching.
Never let a maximum success feel like a ceiling. There is always something beyond it.
4. Signature Skills
Every major NPC and trader has one non-Persuasion skill that bypasses the normal tier structure when the character has it. This rewards investment at Session 0: a character who built their Medicus around Medicine proficiency gets instant standing with Valeria that another character would take three sessions to earn.
In practice: The signature skill is listed per NPC in the relevant reference. It typically functions as an auto-advance of one tier (no roll required) or as a significant DC reduction (-4 or better). A character can only benefit from their signature skill once per NPC; after that, the relationship is set.
5. Investment Checks
Some checks cost a resource in addition to the roll: time, coin, reputation, a specific item, or an action. Spending the resource is the signal that the character is serious. The roll determines how well it goes.
In practice: Paterculus gives better augury to someone who sits through the full ceremony (30 minutes, skips a downtime action) than to someone who asks for a quick reading. The time investment signals sincerity; the roll determines whether Mars is listening. Document investment options per NPC alongside standard checks.
6. Temporal Gates
Certain checks are only available at specific moments. Miss the moment, miss the check permanently. These create urgency and make information feel like a real resource that can be lost.
In practice: Tribune Lucius is uncertain about his mission exactly once: during Scene 3 of Session 2, when his instructions from Brutus conflict with what he has seen the party do. A DC 14 Insight check during that scene reveals his hesitation. After Scene 3, the window closes. If the party never interacted with him closely enough to notice, that information is gone.
Document temporal gates explicitly: what session, what scene, what the check reveals, and what it costs to miss it.
7. Tier Memory
The relationship system remembers. A check that fails at DC 15 is not automatically available next session. Re-approach conditions must be earned: something has to happen that gives the character standing to try again.
In practice: If a player tries to deceive Varro and he catches it, Varro’s internal state shifts to “watchful.” The next Persuasion check with him is at +3 DC permanently, and the DC 13 approach that might have worked is now DC 16. Recovery requires demonstrating military competence in front of him (a specific action, not another roll). Document re-approach conditions per NPC.
How to Use This System at the Table
Before each session: Read the per-session NPC states in gm_intro.qmd and camp_economy.qmd. Know where each NPC’s relationship tier currently sits for each party member. Note any temporal gates that open or close this session.
During play: When a player attempts a skill check against an NPC, ask yourself four questions:
- Is this a signature skill moment? If yes, auto-advance and describe the NPC noticing the competence.
- Is there an investment option? If the player is spending something, that signals engagement; reward it.
- What tier is this NPC at for this character? Adjust DC by the relationship modifier.
- What does failure open? Know this before you call for the roll.
When players try unexpected approaches: Most creative approaches map to one of the principles above. If they do something clever and unexpected, lean on “wrong tool, different door”: they get a result that is genuinely useful, just not the one they expected. If you are unsure what that result is, buy 10 seconds by having the NPC pause before responding.
Relationship DC Modifiers (Quick Reference)
Full table in reputation.qmd. This is the DM table version.
| Relationship Statement | DC Modifier | Special Access |
|---|---|---|
| “They do not know you” | No modifier | Baseline service only |
| “Professional dealings, nothing more” | No modifier | Standard service; nothing off-ledger |
| “They owe you something small” | -2 | One non-standard piece of information or service |
| “They consider you an ally” | -4 | Access to the NPC’s real usefulness; things not on any ledger |
| “They owe you something real” | -6 | One automatic success per session (DM chooses which); cascade unlocks available |
Signature Skills by NPC
| NPC | Signature Skill | Effect |
|---|---|---|
| Corvinus | History DC 14 (his career) | He notices you know his record; gives advantage on one Persuasion per session but makes him wary |
| Cassia | Religion DC 13 | Full information access; she speaks without filtering to someone who understands the gods |
| Varro | Athletics DC 12 or military tool proficiency | Auto-advance to Trusted tier; he evaluates by capability, not words |
| Tribune Lucius | Insight DC 15 (session 2 only) | Reveals his moment of doubt; opens negotiation option that otherwise does not exist |
| Vercingetorix | Germanic language proficiency | Auto-advance; also unlocks two additional dialogue options in Session 2 |
| Quartus | Military supply knowledge (History DC 12 about logistics) | He treats you as a peer; gains advantage on checks to access off-ledger information |
| Rufus | Smith’s tools proficiency or Athletics DC 12 | He evaluates by how you handle equipment; auto-advances to Trusted |
| Valeria | Medicine DC 13 | Peer-to-peer respect; instant Trusted tier access and she shares her symptom documentation |
| Paterculus | Religion DC 12 with genuine question | He responds to people who actually want to understand; Trusted tier for the session |
| Cato | Insight DC 13 or Performance DC 11 | He chooses to talk; the barrier drops because you found the story he wanted to tell |
| Sigrun | Germanic language proficiency or Survival DC 14 | She knows you are not a city person; immediate advance past the first tier |
Temporal Gates Master Table
| Check | Available | What it reveals | Cost of missing it |
|---|---|---|---|
| Corvinus’s real agenda | Session 1 only, before Tribune arrives | He is gambling-debt controlled; this changes every future interaction with him | You negotiate with Corvinus without knowing his actual constraints |
| Tribune Lucius’s doubt | Session 2, Scene 3 only, DC 14 Insight | He has been given a script he is not fully committed to; negotiation path opens | You cannot negotiate with Lucius; only confront or avoid |
| Mad worker’s behavior pattern | Session 1, Scene 2-3 only, DC 13 Insight | He has been showing pre-attack signs for hours; preparation is possible | Scene 4 encounter is a surprise |
| River crossing boot print | Session 3, river crossing scene, DC 11 Perception (watching bank not river), 1 round only | Legate’s advance scouts were here an hour ago | Party does not know they are being tracked |
| Vercingetorix’s dying admission | Session 3 only, after grove ritual | He has known where Brutus’s plan leads and chose not to tell the party; explains why | The Session 4 betrayal revelation lands without context |
| Cassia’s true identity | Sessions 3-4, after party does something genuine in her presence | She is Mars’ daughter and can feel the spear; changes every divine interaction | You interpret her warnings without understanding their source |
| Patrol boot print | Session 3, river scene, 1 round only | Corvinus has scouts ahead of the party | Party walks into the ambush blind |
| Cato’s Lucius connection | Session 2-3 only, before Cato chooses a side | Lucius approached him; Cato has not answered; the party can influence his decision | Cato chooses without party input; may default to safer option |
Failure States Reference
What failed checks open rather than close.
| NPC | Failed approach | What it opens |
|---|---|---|
| Quartus (Persuasion fails) | Official channels: slower, auditable, Corvinus may notice the request | Paperwork trail that becomes evidence in Session 3 if Corvinus investigates |
| Quartus (bribery attempt) | Permanent wariness; all future DCs +2; he files a mental note | The second ledger becomes unreachable except through trust |
| Rufus (Persuasion without work to show) | Minimum service, no guarantee, no conversation | A mechanical result with no relationship advancement; neutral |
| Valeria (rushed or demanding) | Clinical mode: she treats you like a difficult patient | Limited information, standard prices, no access to documentation |
| Valeria (Intimidation) | Sends for Corvinus; will not treat the character again that session | Medical lockout; must find field medicine or healing spells |
| Paterculus (dismissive of omens) | Public augury only: DC 13 result maximum, no personal interpretation | Accurate but incomplete; misses the context he would give someone he trusted |
| Cato (direct demand without relationship) | Surface gossip only; he charges the premium price for the lesser information | Accurate but shallow; he is not lying, he is rationing |
| Cato (authority invoked) | Professionally sealed; perfect service, nothing useful | A good meal and a polite conversation that goes nowhere |
| Sigrun (authority or demand) | She leaves; relationship resets to baseline | Does not return until a trusted character makes contact |
| Varro (Deception, caught) | Permanent watchfulness; all future DCs +3; recovery requires action not roll | A changed relationship that can only be repaired by demonstrating competence |
| Corvinus (Persuasion, strong failure) | He files it as insubordination; formal military consequence pending | A threat hanging over the party that Brutus or Lucius can activate |
Investment Check Options
Spending a resource earns mechanical advantage. Each investment option is available once per NPC per campaign.
| NPC | Investment | Mechanical effect |
|---|---|---|
| Quartus | 1 hour helping with inventory count | Advantage on next Persuasion check; he remembers who helped without being asked |
| Quartus | Bring him an item from the ruins not on the official manifest | He shows you the second ledger voluntarily (no check required) |
| Rufus | Bring iron ore from the forest | Auto-advance to Trusted; one weapon upgraded to +1 for free |
| Rufus | Offer to work the bellows for an hour (Strength-based work) | Advantage on all skill checks with him for the session; he talks while working |
| Valeria | Assist with a procedure without being asked (hold the patient, hand implements) | Advantage on all future Medicine checks when she is present; she shares one documentation page |
| Valeria | Deliver medicinal herbs from the forest (any bundle) | Trusted tier access for the session; she names the plants for you |
| Paterculus | Attend the full morning ceremony without being asked (30 min) | Trusted tier access for the session; he speaks without filtering |
| Paterculus | Bring a rune carving for him to interpret | Second augury available this session (DC +2); he is engaged |
| Cato | Buy a round for the off-watch soldiers at his bar | Advantage on Persuasion with him for the evening; normal rules next session |
| Cato | Come back three sessions in a row without asking for anything | Relationship advances to “they consider you an ally” automatically |
| Sigrun | Trade any forest-sourced material at below-market price without being asked | Relationship advances one step; she knows you understand the forest has value |
| Sigrun | Offer amber at cost to Paterculus in her presence (letting her see you value it properly) | She volunteers that she can identify rune inscriptions; cascade unlock triggered |
Skill Combination Rules (GM Reference)
The player-facing descriptions are in skills.qmd. This section gives you the mechanics you need to adjudicate combinations quickly and consistently at the table.
General rule: Combinations require both participants to be in the same scene. Each rolls separately. The combination produces an outcome that neither character could reach alone; it does not simply double the chance of success. If only one succeeds, the combination produces a degraded but non-zero result. If both fail, each character’s failure state applies individually.
Athletics and Testudo (3+ characters)
Prerequisite: At least 3 characters each succeed on DC 12 Athletics as part of entering Testudo (bonus action; same action economy as forming Testudo).
Full combination: Cover increases to full cover; one interior character may use their action to perform DC 10 Medicine (1d4 HP) or DC 14 Medicine (1d8 HP) on an ally inside the formation.
Partial (1-2 succeed on Athletics): Standard Testudo rules, no enhancement.
Breaking: Standard Testudo break conditions from roman_tactics.qmd apply. An attacker with Athletics +5 or higher has advantage on the DC 14 grapple check against the corner-man of an enhanced formation.
DM note: Track which characters declared Athletics. If the party habitually uses this combination, a prepared Germanic opponent may specifically target the weakest Athletics character in the formation on subsequent rounds.
Perception and Stealth (paired patrol)
Prerequisite: Watcher succeeds on Perception (DC 11 baseline, DC 14 in ruins when spear influence is active). Mover succeeds on Stealth vs. passive Perception of targets in the space.
Full combination: Party learns all creatures and objects in the space without triggering any reaction-based alerts or prepared ambushes targeting movement noise.
Partial (Perception only): Watcher spots the threat; mover does not know in time. Half information yield; mover may be surprised if a threat acts.
Partial (Stealth only): Mover passes undetected; does not know what they passed through. Zero information from the pass.
Both fail: Standard exploration rules; no combination benefit; watcher’s failed Perception roll alerts creatures who make Perception checks against the party’s noise.
DM note: The watcher cannot move on the round they are watching. This is a real cost in session 4 where speed matters. If the party tries to designate the same character as both watcher and mover, that is not possible: watching requires stillness.
Persuasion and Insight (tag-team interrogation)
Prerequisite: Players A and B must both be in the scene. Insight is the bonus action on Player A’s turn; Persuasion is the action on Player B’s turn (same round or immediately following).
Full combination (Insight succeeds): Player B gains advantage on Persuasion roll; target’s effective DC is reduced by 2.
Partial (Insight fails by 4 or less): Player A reads nothing useful. Player B rolls Persuasion without advantage but at normal DC.
Failure (Insight fails by 5 or more): Player A misreads the target. Player B’s Persuasion DC increases by 2.
DM note: The misread failure is important. Do not fudge it. If Player A guesses wrong and Player B argues for the wrong thing, the NPC becomes defensive: they feel the conversation is not about them. This is not a wall; it creates a different scene. The NPC closes off the direct approach but opens a question: “Why do you think I care about that?”
Religion and Medicine (ritual healing)
Prerequisite: 10 minutes; not in active combat. DC 15 Religion then DC 14 Medicine in that order.
Full combination: Normal HD recovery result plus 1d6 additional HP. Does not cost spell slots.
Partial (Religion only): Target gains advantage on next death save or stabilization check.
Partial (Medicine only): Normal healing, no bonus. The Religion attempt that failed does not penalize Medicine.
Both fail: Medicine check at disadvantage. The incorrectly invoked rite created anxiety rather than calm.
DM note: This combination is specifically designed for the siege phase (Chapter 4) where magical healing may be rationed and long rests are unavailable. If the party discovers it during Session 1-2 and develops the habit, they will use it exactly when they need it most. That is the intended design. Do not nerf it.
History and Investigation (forensic reconstruction)
Prerequisite: History DC 17 must be already recorded from a previous check in this location. This is a cascade unlock: the DC 17 check reveals the existence of the deeper investigation layer, not the layer itself. Investigation DC 13 then extracts it.
Full combination: DM provides two distinct pieces of information from the scene instead of one: the current physical state and the historical transition that produced it.
Partial (Investigation fails): History context is available but the physical evidence does not yield its second layer. The History character may attempt DC 15 History (no advantage) to reconstruct the gap theoretically.
DM note: Prepare the “second layer” for each ruins chamber before the session. The Hall of Shields second layer: the shields were placed here over 80 years by multiple tribal groups; they are votive offerings, not trophies. The Chamber of Chains second layer: the binding was designed for something specific that had previously escaped a different containment; this was not the first attempt. The Vault second layer: the dedication formula was written by someone who knew both Roman and Germanic ritual forms, meaning the builder had access to both traditions simultaneously.
Survival and Nature (extended forest tracking)
Prerequisite: Survival DC 13, Nature DC 12, both in the same tracking scene.
Full combination: Standard tracking result plus one piece of information about the tracked party’s emotional state or urgency, derived from animal and vegetation response to their passage.
Partial (one succeeds): Standard result from the succeeding skill only.
DM note: The emotional state information is not a guess: it is readable from how quickly vegetation was disturbed and what animals did after the group passed. A fleeing group leaves a different mark on a forest than a group moving deliberately. Use this to give players information they cannot use to confront the tracked party directly but can use to prepare for what they will find.
Stealth and Deception (planted information)
Prerequisite: Stealth DC 14 (placing); Deception DC 13 (framing, made in advance).
Full combination: Object is found by the intended person and interpreted as the party intends.
Partial (Deception fails): Object found by intended person; they are suspicious rather than convinced. They investigate the frame rather than accepting it.
Partial (Stealth fails): Object found too soon, by the wrong person.
DM note: The Deception check represents the party setting up the context for how the object will be found and what it will look like. This requires them to know enough about the target to predict their behavior. If the party tries to plant information on a character they have not interacted with, call for a DC 12 Insight check first to see if their prediction of the target’s behavior is even plausible.
Performance and Intimidation (crowd pressure)
Prerequisite: A group or crowd scene; DC 12 Performance then DC 11 Intimidation.
Full combination: Target must comply publicly or publicly refuse. A public refusal has its own social cost in the scene: it isolates the target from the crowd’s approval.
Partial (Performance only): Crowd attention and framing established; follow-up Persuasion by any party member gains advantage for the rest of the scene.
DM note: This combination does not work on NPCs of higher military rank than the intimidating character without formal military consequences. Corvinus in Session 1 is immune to this approach. Varro is not immune but will remember it and evaluate whether he respects the judgment that deployed it. Use that as a Tier Memory note.
The Knowledge-Chain System: GM Adjudication
Players build toward outcomes through chains of rolls. Your job at the table is to know where each player is in the chain and what the next link costs.
High bonus vs. good roll
Both paths work. A character with Religion +8 who does not roll may still have baseline Tier One knowledge (the no-roll layer). A character with Religion +1 who rolls a natural 20 extracts Tier Three information through luck and effort. Both are valid. Do not penalize the high-bonus character for not rolling: they know things without rolling. Do not penalize the lucky roller: they worked for it. The difference shows up in relationship tiers: the high-bonus character is recognized as knowledgeable by NPCs who can read competence (Paterculus, Cassia, Valeria). The lucky roller extracted the information but the NPC does not know they have it.
Starting bonuses at the table
Cultural starting bonuses (documented in skills.qmd and peoples.qmd) affect the no-roll baseline: a character with Arcana +3 from their Greek background has the Tier One Arcana knowledge already, without a check. Treat this as automatic at the table. When that character then rolls for Tier Two information, their high total reflects genuine expertise rather than luck. Do not call for a roll when the character’s total already clears DC 13 without rolling: they simply know it.
When the chain breaks
If a player attempts the final persuasion step without building the earlier chain links, run the interaction at base DC with no modifiers. Do not explain what they missed: let the NPC’s response reveal that the conversation did not land the way they expected. The NPC is not hostile; they are simply unmoved. “He listened. He nodded. He thanked you for the information. He did nothing with it.” That is the signal that the chain has more steps. The player will figure out what they missed.
When players bypass the chain
Some players will try to shortcut the chain with high Persuasion alone. This is not wrong. It is just a different tool that opens a different door (Principle 2). A DC-beating Persuasion without prior Insight or History produces surface compliance: the NPC does what is asked in the moment. Nothing changes underneath. The NPC does not reveal their real position, their real information, or their real agenda. The party got a result; they did not get the scene. Let that be the outcome and let the players decide whether they want the deeper version.