Translated from the back:
A huge black ship is on its way to Aventurien. Mordor the witch king, ally of the dark powers of the shadow realm, has sent it with a sinister crew.
They are demons, pirates and monstrous mercenaries from the underwater realm Wajahd who steer Mordor's ship through the wild seas. They shall conquer new land by bringing the Soul Diamond ashore. Where ever that will succeed the dark forces will prevail.
There is just one remedy to save Aventurien - the black Soul Diamond, hidden somewhere in a complex labyrith in the vast bowels of the ship, needs to be destroyed. Fearless heroes board the ship! Overcome the fiendish traps under deck. Dreadful monster await but so do abundant treasures ...