I'm thinking AoE fire damage to everyone standing beside the archdemons, that way you could teleport to the middle of the opposing army and dish out some heavy damage, it wouldn't be very effective against demons or dragons but I'm aiming for good, not overpowered. And maybe a self-buffing ability similar to the one dark knights have except it would increase their resistance to damage making them a more effective tank.
This is all assuming that I figure out how to script abilities because right now I don't really get it.