Shrieker
Creature
The Shrieker is harmless in itself, which is precisely what makes it so dangerous: a giant pale fungus of the deep dark that, when light or movement disturbs it, lets out a piercing, carrying shriek that echoes through the tunnels for a very long way. It cannot hurt a soul. What it does is summon - the shriek draws every hungry thing within earshot to come and investigate, and a party that blunders into a Shrieker in a monster-haunted deep has just rung the dinner bell for the entire level. Quiet delvers learn to spot them and give them a very wide, very careful berth.