Encounter-a-Day

While exploring the dungeon, the PCs come to a T-junction with a slight slope. In the up-slope direction, the passage extends about 20 feet into a dead end. Down-slope, it extends 100 feet and light can be seen coming from beyond. The entire passageway is 10 feet wide.

A 10′x10′ trigger plate is located about 40 feet down-slope from the junction; if anyone steps on it, a door slams shut over the original corridor, trapping whoever’s in there on the slope. A moment later, a huge cylindrical boulder drops at the top of the slope and begins accelerating towards the PCs. The boulder is 10-feet wide and 10 feet in diameter, filling the tunnel from side to side and leaving only a few feet between it and the ceiling.

At the end of the tunnel, where lights can be seen, a gelatinous cube waits, filling the doorway. Due to the refraction of the lights streaming in from behind it, the gelatinous cube is easier to spot than normal (DC 20 perception check instead of DC 25). A counter-weighted trap door at the end of the hallway collects the boulder in a storage area beneath the hallway, preventing the boulder from splattering the gelatinous ooze.

Level 5 Obstable, 200 xp (doesn’t include experience for gelatinous cube)

Trap: A boulder runs the PCs down, damaging them and herding them into a waiting gelatinous cube.
Perception:

• DC 12: The character notices the hole from which the boulder drops at the top of the slope.
• DC 22: The character notices the trigger plate.
• DC 17: The character notices the trap door the boulder falls into at the end.
• DC 25: The character notices the gelatinous cube at the end of the hall. Characters within 6 squares of the cube get a +5 circumstance bonus to this check due to the refraction of the light passing through the cube’s body from behind.

Initiative: +7
Speed: 4
Trigger: A character steps on the trigger plate.

Attack
Free action, whenever the boulder moves into a creature.
+10 vs. Reflex
Hit: 2d8+4 damage, and the target is knocked prone. Additionally, the target is pushed along with the boulder, ending in front of it down-slope.
Miss: As hit, but half damage and the target is not knocked prone.

Countermeasures

• A character can jam the trigger plate, allowing safe passage. DC 17 Thievery. Complexity 1 skill challenge (4 successes before 3 failures). Success prevents the door from jamming shut or the boulder from dropping, though the gelatinous cube is still at the end of the tunnel. Failure triggers the trap.
• A character can try to hold the boulder back. Stopping it after it’s started rolling required a DC 22 athletics check. Keeping it stationary after it’s already stopped requires a DC 17 athletics check.
• Characters may force the trap door at the end of the hallway open with a DC 17 athletics check. Inside there is ample room to hide and dodge the boulder when it falls.
• Characters may defeat the gelatinous goo or otherwise bypass it.