The most dangerous skill at the moment is Time Stop, which prevents one of your units from acting; it's an advanced form of blindness. Why advanced? Because it cannot be dispelled and is not dispelled when attacking this unit. This ability is located in the Primal Magic branch and requires 55 mana. It can be cast once per battle, but that doesn't make it any safer.
The next extremely useful skill for a mage is Meditation, which increases magical power (also known as spell power) by 20 units for 4 turns and, unfortunately, restores only 15% of mana (it was 50% in the beta). With +20 magical power for 4 turns, you can do a lot. It costs 30 mana to cast, so always remember to leave those 30 mana to restore 15%. It is located in the Primal Magic branch.
In the same branch, there are 2 more good spells: Explosion, which deals unrecoverable damage (i.e., you cannot heal it), and Teleportation. Both cost 45 mana.
Yes, all of the listed abilities can be upgraded starting from level 15.
Since we're talking about skills, I won't describe abilities that add magical power and mana.
In Dark Magic, only Vampirism and its mass version caught my attention. In the beta, health regeneration occurred even with ranged attacks; I don't know how things are in the release yet. It's a very useful skill.
The damage-dealing skills disappointed me due to the absence of Warlocks.
Асха все обращает на пользу... :smile16: