Why don’t you play as the Academy?

A Mage becomes a powerful Mage after level 30+ and when they have a larger army.
At level 30+, use the "All-Seeing" spell, combined with "Counterspell" and "Mirror Image." It's very difficult for Warlocks and Undead to deal with. The Mage moves so quickly that they can cast "Counterspell" and still have time to cast other spells (and "Mirror Image" can create surprises for the opponent).
Before level 30, the troops have weak stats, similar to Undead. Their attack and defense values are low.
I level up the "All-Seeing" spell. I don't understand why you need libraries and other magic skills; it's difficult, but once you've leveled up this super ability, you don't have to worry about finding spells.