I discovered new tactic!!!

[Elwin]

NOt really demons are way mor effective, griphons do low damage and demon do quite much, especialy to units 1-3 (20k crits while in pentagram was quite normal in late game). Yes they are slow but there are some ways to pet them directrly into your enemies .. Personally i just teleported him at beggining of fight, my brother was swaping him with enemy archers with demoness infernal exchange ability( and with onslaught 3 anga's ruby demoness always go first )