ToME: the Tales of Maj'Eyal

I am trying to figure out how I died. I was a necromancer and I was killed and turned into a lich. I then fled up a level and died permanently. The death message says i failed the "lich resurrection ritual".

any assistance would be appreciated.

"Failed to complete the lich resurrection ritual" means that you died as a Lich, Neverending Unlife let you resurrect but you failed to meet it's requirement of killing a unique or higher rank enemy within X turns, and you died proper.