Crookshank

Crookshank is a very dangerous hostile creature that may spawn through monsters portals above the ground in multiplayer games.

Behavior
In general it behaves like a regular zombie.

Attack
It has a single-target melee attack from its open belly that causes a knockback effect.

Mobility
It can not climb walls, but can jump one block at a time, also taking advantage of skeletons in a shield stair position to climb higher cliffs.

It can fall from a ten block height without being hurt.

You've been digested achievement
There is an Steam achievement related to the crookshanks called You've been digested!. A low health dwarf must die insinde a crookshank's tummy.

It's hard to get this achievement, because low health dwarfs will flee from danger and get to safety or die to unpredictable reasons, and direct controling dwarfs in multiplayer games does consume a lot of mana. Also, it's possible to have several waves without a single crookshank or waves with so much enemies that it becomes impossible not to kill the crookshank among them.

Just playing a lot of multiplayer games in harder difficulties or multiplayer games with everynight raids is recomended to get this. The probability though of don't even seeing the dwarf dying is high.