Black Ark

The largest vessels that the Elven Corsairs command are the infamous Black Arks, vast floating fortresses capable of carrying thousands of warriors and slaves. Their sorcerers summon beasts up from the deep which fortifications are then built on. These ‘living ships’ always travel with a Black Ark, and drive fear into the hearts of all the corsairs would prey upon.

Source

 * Warhammer Fantasy RPG 2nd ED -- Old World Bestiary (pg. 42)