Basium cast his world spell and killed Hyborem. Lucky him, wasn't all too worried about it as I had my immortal promotion, unfortunately his world spell apparantly doesn't allow hyborem to respawn with immortal. It would be nice to not allow Basium to damage Hyborem himself with it, it's nasty enough as it is killing off all the defenders in 75% of my cities with one spell.
On the up side, the code that removes the leader traits after Hyborem is dead is working correctly, and Hyborem dropped Orthos' Axe in the square he died in and didn't take it to the void with him.
EDIT: Hyborem still had his immortal promotion meaning he hadn't died yet, i realize he's not actually immortal.