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The situation
The party reaches a timber-braced blast chamber just as a panicked goblin foreman realizes that two fuse lines are burning toward the wrong powder stores. Three miners are trapped behind a jammed ore cart. Green crystals in the eastern wall pulse whenever magic is cast nearby.
This isn't a puzzle with one correct answer. It's a pressure cooker. The party wins by getting the miners out and stopping the blast, or just by getting everyone out before it goes off.
Read aloud
The tunnel opens into a low chamber webbed with timber supports and mine-cart rails. Two orange sparks hiss along black fuse cord in opposite directions. Behind an overturned ore cart, someone is shouting for help. On the far wall, green crystals brighten in time with the crackle of magic in the air.
What everyone can see
- Fuse A burns toward three powder barrels beside the western support frame.
- Fuse B heads for a sealed crate marked with a crude goblin skull.
- Three miners are trapped behind a jammed ore cart.
- Two goblin bombers are arguing about who was supposed to light which fuse.
- The crystal wall hums a little louder every time somebody casts a spell in the chamber.
The countdown
| Round | What happens at the end of the round |
|---|---|
| 1 | The western support groans. Dust falls. Everyone understands the chamber is unstable. |
| 2 | The crystal wall flashes. The next spell cast in the chamber causes a harmless but violent shockwave that shoves nearby creatures 5 feet. |
| 3 | Fuse A reaches the last ten feet. A creature can stamp it out, cut it, soak it, redirect it, or move the barrels. |
| 4 | Any fuse that has not been stopped reaches its target. Resolve the blast, then start the collapse sequence below. |
Actions that matter
Use whatever checks fit your system. For 5e-style play, DC 11–14 is enough for most actions. Strong ideas can simply work.
- Free the miners. Lift the cart, repair the wheel, break the pinning timber, or just talk them into squeezing through a gap.
- Stop a fuse. Cut it, smother it, soak it, redirect it, whatever the character would actually try.
- One barrel can be dragged away each round. Two characters working together can move the whole crate.
- Stabilize a support by wedging it with tools or timber to buy time before the collapse.
- One bomber wants to run. The other insists he can "fix the explosion" if somebody gives him ten seconds and a hammer. Talking to them is a real option too.
Goblin bombers
Use ordinary goblin statistics if you want combat. Each bomber carries one small blast charge. Instead of attacking, a bomber can throw it at an empty square within 30 feet; creatures adjacent to the square make a modest Dexterity save or take roughly the damage of a basic goblin attack plus 1d6 fire. A blast also interacts with the environment.
If the party offers a believable escape route, the frightened bomber surrenders immediately. The stubborn bomber surrenders if the party prevents one explosion.
Crystal resonance
After any leveled spell is cast within 20 feet of the green crystal wall, mark one resonance. At three resonance, the wall releases a pulse at the end of the current turn. Everyone within 15 feet is pushed 10 feet away; unsecured objects slide or roll with them. The resonance then resets to zero.
Players can deliberately exploit this to move the ore cart, shove a powder barrel away from a fuse, or launch a goblin off a platform. Reward the idea.
If the powder explodes
An explosion should be serious but not automatically end the encounter. Creatures close to the target make an appropriate save for moderate fire/bludgeoning damage. Then the chamber begins collapsing.
| Collapse round | Complication |
|---|---|
| 1 | A support breaks. Choose one route out; it becomes difficult terrain. |
| 2 | Falling debris forces everyone still inside to move or risk damage. |
| 3 | The chamber comes down. Anyone still inside needs a final escape check or is trapped rather than killed outright. |
Rewards
- The rescued miners know a safe route through the next section of mine.
- The surrendered bomber can identify the person who ordered the demolition.
- An intact powder crate can become a one-use environmental tool later in the adventure.
- A fist-sized crystal fragment glows near active magic and can be sold or studied.
How to scale it
Easier: start with only Fuse A lit, and let the miners free themselves after two successful party actions. Harder: add a third fuse to a support column, or put one hostile creature on a raised walkway where it can cut off escape routes.
Goblins GO BOOM
The complete level 3–5 adventure adds a runaway mine-cart chase, multiple mine locations, custom enemies, maps, tokens, rewards, and a two-phase collapsing finale.
See the full adventure ↗