Morphius, from Ultima Underworld II
Morphius was discovered by Praecor Loth as a thief living in horrible conditions. Loth saw his talents and trained him to become a master assassin and perfect spy. Mophius became so thankful that saw Loth as his saviour who he wanted to share with no one, particularly starting to hate his wife Helena. So when Praecor Loth died, he, like Lethe and Lord Umbria, had become literally addicted to his king. He couldn't imagine existing without him, so the mage Lord Umbria turned all three of them into Liches and they held the soul of their dead king on the world, egoistically serving their need to have him around and denying everyone else their peace.
Over the years Morphius killed many of the Guardian's followers. So when the Avatar met him in Ultima Underworld II, he accused the intruder of working for the Guardian as well. It was impossible to convince him that this wasn't the case and after making it clear that Loth deserved his peace, Morphius blew his lid and screamed like a kid that was denied his candy, that no one should ever again take him away from them, before attacking.
The Avatar slew him and his essence was destroyed for all time. Ironically his egoism in the end prevented him from being with his king in the afterlife.
- Morphius seems to slowly fall apart, exactly like Lethe. Only Lord Umbria seems immune to it. Probably, the transformation into Liches doesn't work so well on non-mages.