Sorry about the late article, but I severely blanked when it came time to write. I guess that's a symptom of having moved on from 4th edition to D&D Next play-testing. BUT! The show must go on until D&D Next is officially published.
There was a time when I was planning my Magnum Opus; a campaign to bridge the gap between 4th Edition and the Next Edition. The following was to be in the very first series of encounters: The Cave Swarm Hazard!
Cave Swarm Hazard
Something deep in the cave has spooked the native wildlife. They are now in a mad dash for the exit. Watch your step.
Cave Swarm; Level 1 Obstacle
Hazard; XP 100
The squeaks and scratches of the approaching swarm are your only warning before the vermin overtake you.Hazard: A swarm of scared cave creatures covers the floor, attempting to escape from something further in the complex It lasts until the end of the encounter.
PerceptionDC 12: The character notices the coming swarm, gaining a +2 bonus to all defenses against the hazard's attack.
TriggerThe swarm makes its attack when a creature begins its turn on the floor.
AttackImmediate Reaction; Melee
Target: The triggering creature
Attack: +4 vs. Reflex
Hit: 1d6+3 damage
Special: Minions are only weakened by this attack.
CountermeasuresA character can avoid the hazard by climbing walls, stalagmites, and rocks to keep off the main floor. The creatures of the swarm are too eager to escape to take the time to climb these surfaces.
The Cave Swarm was designed for Dungeons and Dragons 4th Edition by Wizards of the Coast.