Pheonix bug

[Srydalsaint]

Hiya
I have the latest build installed 6250, bought the game on steam.

I'm stuck on the mission to get the staff of starlight which i assume i need to do in order to progress. My problem is when I fight the master nilrim wizard guy (after you beat the three altars and release the forcefield on the mages place) he always casts the summon pheonix spell. It always bugs out after you kill it when it ressurects you can't hit it again. You kill all his other troops and that damn rezzed pheonix just stays in the same place defending every round. The only thing i can think of to get round it is to be lucky and hope he doesn't cast that spell. He always does though.
What i was thinking was that maybe if i could 'cheat' and modify one of my spells to instakill any troop i could probably make it through the fight quick enough. I've been looking for guides on how to do this but haven't had any joy so far. Can anyone think of any kind of workaround for this.