In general, this is the battle tactic against Godric, with the Necromancer's Sign, raising the dead, blindness, suggestion, battle frenzy, and phantom spells.
First, mass slow down, then apply the Necromancer's Sign to the Harbingers. And move them towards the gate. Usually, the golems that appear out of nowhere open the gate. Let the Harbingers fight them. Try to group the rest of the units. Raise Harbingers as needed. Eventually, they will deal with everything. Leave 1-2 blinded titans for the finale. By this time, Godric should have spent all his mana.
Phase two. Move the Harbingers towards the catapult. Markel casts earthquake a couple of times to destroy the towers. And starts creating phantoms. Godric, of course, periodically swings his iron weapon, but doesn't always hit the phantoms, and Markel casts spells more often. After creating enough phantoms, we kill the remaining titans. An ambush unit appears. We slow down everyone. Then, we cast battle frenzy on the paladins, and they destroy all the archers. Then, we cast battle frenzy on the angels, and they destroy all the paladins. Then, we cast battle frenzy on the swordsmen, and they start fighting the angels. When the swordsmen are gone, I still had about 90 angels left. Blindness and phantoms dealt with them effectively.