How to take down this pesky pretender?

[NTJedi]

Loren said:
I was having quite a bit of trouble taking down a pesky pretender. He was a wyrm with some pretty good stats. Repeated attempts to kill him always failed. I had a lot of gems, I decided on a different tactic. I wished my prophet (my pretender was immobile) up to some pretty insane levels, gave him 400 ancient ones and an ethereal crossbow with orders to attack rearmost (he had a precision over 40, he should have hit!) He never fires. I script shadow blasts--a few turns into the battle he drops one into my troops, never fires one at the pretender. I tried a few other spells, same effect. I was about to try sending him in alone (the wyrm never had more than a few units and my guy was tougher) when I got a dominion kill.

Other than dominion, how in the world should I take down a pest like this? He was powerful, regenerating, good MR, poison immune and a good spellcaster with a full load of gems. I simply couldn't do anything to him, in time my forces would rout.

If you have the gems to be wishing your prophet up high levels then you have plenty of power/gems for killing a wyrm especially if its a SP game.
First should be a setup for preparing him to be killed which means you're casting horror marks and curse on him. His magic resistance won't work here. The curse means the wyrm will more quickly acquire afflictions and your enemy pretender can never have too many horror marks.
Second if this creature isn't using cold or heat resistance then send stacks of winter wolves OR summer lions, but not both at the same time otherwise they will cause fatigue on each other. Winter wolves and ghosts can make a strong team.

If the above doesn't work then let us know the magic paths of the pretender and what its casting to survive.