Lich's range units

Lich's range units consist of Acolytes, Occultists, and Warlocks. They have very high damage output but have very short ranged compared to other ranged units such as the archer, unless on the garrison wall, where they have (as any unit on the wall) unlimited range. Their high damage and the fact that they are easy to replace (they share most of the lich's melee units properties on the subject) means they are a good choice to attack walls, specially if their Undead trait is taken into consideration (Undead units excel at plundering resources when attacking city walls). They can be buffed by Gazul’s passives and other heroes have abilities/passives that synergies with them.

Upgrades
The ability of upgrading Acolytes, Occultists, and Warlocks is unlocked at academy level 1