encounter-build

name

encounter-build

description

Build a balanced D&D 5e (2014) encounter using the DMG encounter-building rules — XP thresholds by character level, monster XP, and the encounter multiplier. Trigger when the DM needs to prep or improvise a combat / skill encounter. Loads the active character from campaigns/<slug>/state.md, asks for difficulty and theme, picks monsters, and writes the encounter to campaigns/<slug>/encounters/<slug>.md.

Encounter Build

Build a mechanically balanced D&D 5e (2014) encounter against the active character. Use the DMG (p. 82) encounter-building rules. All official monster sources are in scope (Monster Manual, Volo's, Mordenkainen's Tome of Foes / Monsters of the Multiverse, Fizban's, Tasha's, Xanathar's). Cite the source and CR when listing each monster.

0. Prerequisites

• Confirm mise is available: mise --version.
• Confirm dice work: mise run roll -- 1d20.

1. Load Context

• Determine the campaign slug (from cwd or ask).
• Read campaigns/<slug>/state.md to find the active character.
• Read campaigns/<slug>/characters/<active>.md for level, AC, HP, key features.
• If solo play (one PC), apply the DMG "fewer than three characters" adjustment in §4.

2. Encounter Brief

Bundle the structured choices into a single AskUserQuestion call (per AGENTS.md): Difficulty (easy / medium / hard / deadly), Purpose (random / set-piece / boss / skill challenge), Biome / theme (dungeon / wilderness / urban / planar / etc.). Curate 2–4 representative options per question. Follow up with a plain prose question for Constraints (open-ended: monster types in/out, terrain features, time of day) since that doesn't reduce to a clean shortlist.

3. XP Threshold (Per Character)

Look up the active character's level in this table (DMG p. 82):

Level	Easy	Medium	Hard	Deadly
1	25	50	75	100
2	50	100	150	200
3	75	150	225	400
4	125	250	375	500
5	250	500	750	1,100
6	300	600	900	1,400
7	350	750	1,100	1,700
8	450	900	1,400	2,100
9	550	1,100	1,600	2,400
10	600	1,200	1,900	2,800
11	800	1,600	2,400	3,600
12	1,000	2,000	3,000	4,500
13	1,100	2,200	3,400	5,100
14	1,250	2,500	3,800	5,700
15	1,400	2,800	4,300	6,400
16	1,600	3,200	4,800	7,200
17	2,000	3,900	5,900	8,800
18	2,100	4,200	6,300	9,500
19	2,400	4,900	7,300	10,900
20	2,800	5,700	8,500	12,700

Sum the threshold across the party. With one PC, the party threshold equals the character's threshold.

4. Encounter Multiplier

The encounter's adjusted XP = (sum of monster XP) × multiplier, where:

Monsters	Multiplier
1	×1
2	×1.5
3–6	×2
7–10	×2.5
11–14	×3
15+	×4

Solo / small party adjustment (DMG, "fewer than three characters"): if the party has fewer than 3 PCs, bump the multiplier up one row (e.g., 1 monster → ×1.5, 2 monsters → ×2). For solo play this is the default. Do not apply this adjustment if the party has 3+ PCs; instead, drop the multiplier one row only when the party is 6+.

5. Monster Selection

Pick monsters whose adjusted total XP lands at or just above the chosen difficulty threshold. Heuristics:

• A single monster of CR ≈ PC level often hits "hard" or "deadly" for a solo PC; tune accordingly.
• For solo play, avoid encounters that can stunlock or one-shot the PC (mass save-or-suck, rocket-tag damage). Lean toward monsters with attack-roll abilities the PC can react to.
• Mix roles: a brute, a skirmisher, a controller, a minion swarm. For solo, two complementary monsters often play better than one big brute.
• Note legendary actions, lair actions, and recharge abilities — they raise effective difficulty without raising CR.

If the player wants randomness, build a small d6 / d8 table of candidate monsters and roll: mise run roll -- 1d6.

6. Stat Block & Tactics

For each monster, record:

• Name, source (book + page), CR, XP.
• AC, HP (max or mise run roll -- NdM+K for variable HP), Speed.
• Key attacks (to hit, damage, special effects).
• Saves, immunities, resistances, vulnerabilities, senses, languages.
• Notable traits (Pack Tactics, Magic Resistance, Multiattack, etc.).
• Spells / legendary / lair actions if present.

Tactics: 1–3 sentences on how this monster fights. What it opens with, what it avoids, when it flees or surrenders.

7. Terrain & Setup

• Map sketch in text: rough dimensions, key features (cover, elevation, hazards, light level).
• Starting positions of monsters and PC.
• Environmental hazards (DMG ch. 5) — falling, suffocating, falling rocks, etc.
• Surprise / initiative modifiers (Stealth vs. passive Perception).

8. Treasure

Roll loot per the DMG individual / hoard tables for the encounter's CR tier (DMG ch. 7, p. 133–149). For a quick award, use mise run roll -- <expr> against the appropriate table (e.g., CR 0–4 individual: 1d100).

9. Persist

Write to campaigns/<slug>/encounters/<encounter-slug>.md using the template. Choose a slug that's descriptive (e.g., goblin-ambush-on-the-cart-road).

Do not mark the encounter as "used" yet — that happens when a session log references it.

Every file written must follow the File Conventions in AGENTS.md (final newline, LF, UTF-8, no trailing whitespace).

10. Confirm

Read back: difficulty target, monsters chosen with CR/XP, adjusted XP vs. threshold, terrain summary. Ask the player if anything should change. Apply edits, save.

---

Template

# {{Encounter Title}}

- **Campaign:** {{slug}}
- **Difficulty target:** {{easy | medium | hard | deadly}}
- **Party threshold (XP):** {{N}}
- **Adjusted encounter XP:** {{N}}
- **Multiplier applied:** ×{{m}} (solo adjustment: {{yes | no}})
- **Created:** {{ISO date}}
- **Status:** prepared

## Brief

{{one-paragraph setup: where, when, why}}

## Monsters

| Monster | CR | XP | Source | HP | AC |
| --- | ---: | ---: | --- | ---: | ---: |
| {{name}} | {{cr}} | {{xp}} | {{book p. N}} | {{hp}} | {{ac}} |

### {{Monster Name}} — Stat Block

- **Speed:** ...
- **Saves / immunities / resistances:** ...
- **Senses:** ...
- **Traits:** ...
- **Actions:** ...
- **Tactics:** ...

## Terrain

- **Dimensions:** ...
- **Features:** ...
- **Light:** ...
- **Hazards:** ...

```
[ascii map sketch if helpful]
```

## Initiative & Surprise

- {{notes on stealth, surprise, lighting}}

## Treasure

- {{loot rolls / fixed treasure}}

## DM Notes

- {{anything the player shouldn't see in advance}}