Ranger - "Higher Vampire" [5th Campaign, 5th Mission]

regarding mana, I'm shocked myself; I have no idea where it could have gone:(

Added 1 hour 40 minutes later
damn, he has 3k demons now, that explains where my mana went:( and what should I do now? he already has 14,000 skeletons, it's insane. He's even making phantoms out of them and killing me without any effort.