ToME: the Tales of Maj'Eyal

Daikara. I face the essences and kill them. Then I killed Harkor'Zun.
I step to the next level of the zone...and I find the essences *again*.
However, after I killed them, Harkor'Zun didn't show up - thus the game knew about it having been killed, but not about the essences...

The Essences are not a boss, just an unique. Same happens with the unique undead mold... You can encounter it multiple times, even if it's "unique".

This probably shouldn't happen, otherwise being unique is not being unique.