Undeath mod help

[Cabbo]

So what do I do after killing Antioch? I found the jewelled skulls and killed the ancient Lich but I have no clue what to do now.

[The Water King]

if you saved the arkay priest, nothing. Mod's done.

if you killed the arkay priest, there's an alter that has a book on it that's titled "Arkay the enemy," you put the heart in that alter, there's a stone door that opens, you go in and pull the chain, and go back to the alter and the gate nearby will open. walk through the gate and you'll find a black book that will take you to apocalyptia

[The Water King]

not sure how helpful that is, literally been a decade since you asked, but there's an answer to your question