Level 0 Three sections
Keep formerly ruled by chaos lords, Molan and Felan, now populated by beastmen who seek to resurrect a chaos lord. They kidnap villagers and use them as sacrifice, or convert them to beastmen.
The keep on the surface has multiple ingresses, and interactive things to explore: gatehouse with a dropping portcullis, a well that transforms those who gaze into it into a beastman, a condemned and seal burned down church ignored by the inhabitants.
The underground area is very linear, with a pool with lawful skull grenades, a longship that plies a leviathan-infested sea, and a ziggurat where the villagers are sacrified and the chaos lord is resurrected.
The keep on the surface would be easy to extract and use elsewhere. Nice ideas for encounters: the well, the abandoned church, the pool of lawful grenade skulls, Felan's tomb
There is a table for random generation of beastmen.