Hey DGDobrev, thanks for the save. With it I managed to kill all the guards somehow. The elven stack was easy but the human was so freakin impossible.
The books of evil were so useless that in the end I killed the hordes of priests and archers mostly with poison skulls and incredible luck. At 1 point I was with 1 vampire bat with only 1 hp
I also used the 1 book of evil scroll(to slow the melee) and 1 slow scroll. I made the mistake not to take Diversions skill and also ended up with only 34 mana.
I dont see how you can win with books of evil since thay die so fast from the melee and their dmg is not that great. Even if rank 2 book manage to cast 2 lighting spells on the range units, it's still not enough to hurt them.