Alright, I feel quite a few problems with this creature already, too powerful. Even with a high payday, that can easily be fooled.
Level 1 - Melee Attack/Fireball
Level 2 - Slow
Level 3 - Lightning
Level 4 - Drain
Level 5 - Freeze
Level 6 - Hailstorm
Level 7 - Disruption
Level 8 - Skeleton Army
Level 9 - Disease
Level 10 - Word-of-power
Change the spells to something like this, thus taking out Disease, Skeleton Army, Word-of-Power, Freeze, and Hailstom because those don't seem to fit too well with this creature. Replace Lightning with Invisibility as he seems to be that type of creature.
Level 1 - Melee Attack/Fireball
Level 3 - Slow
Level 5 - Invisibility
Level 7 - Drain
Level 9 - Disruption
Maybe make him not the best researcher as the warlock is for the evil side.
And no creature should need 100 tiles of a room, that means 4 25 by 25Treasuries. But this may not matter as he also needs a Temple, which may cause you to have more Treasuries. I'd change it to 75 tiles, at least.
Looks cool though. I think he should be able to see the invisible, not because he's a giant eye, but because "No one can hide from him".
Edit-
You know, this reminds me of the ghost. Perhaps he could be some kind of upgraded ghost that is more pricy and rare. This wouldn't totally render the ghost useless like the Demon Spawn because of the Dragons.









