The Lich (also known as the Lord of the Dead) is the final boss in the game, and is found in Doomvale, in the 'Throne of Ruin' stage. He is a 'caster' type boss, will not move, and will randomly target units if not being attacked by a melee user.
Lightning Purge - Lightning strikes the boss, doing very high damage to all nearby units.
Meteor Shower - Summons 7 meteors to rain down upon the field, dealing moderate damage and knocking back hit units.
Dark Summon - Summons 2 Black Skeleton Archers and 2 Black Skeleton Knights as the Lich vanishes from the field
Blackout - A unit is randomly targeted and struck by a bolt of lightning, rendering them unable to move or auto-cast. They can, however, still use abilities freely.
The best strategy for killing the Lich is to use a party (group of characters) oriented for maximum damage output (while still using a healer). The key to winning is avoiding his Lightning Purge ability, which deals very high damage to units nearby to him, and can easily kill units (other than tanks). This is easily avoidable. When he is struck by a bolt of weak bolt of lightning, his character will begin to 'stutter', much like the casting animation for the Meteor Shower spell. He will 'stutter' for a very brief period, during which it is strongly adviseable to move all melee units or nearby units far away from him. Once he is struck by a larger bolt of lightning it is safe to return to attacking with melee users. Ranged units (the Ranger, Mages, and the Witch) can all continue to attack him throughout the duration of this spell, and will continue to deal damage to him (despite his health bar dissapearing). Meteor Shower is not an issue unless (rarely) one unit is struck multiple times without being healed. This is easily fixable by using a group heal spell. The Black Skeleton Archers/Knights from Dark Summon are very easy to kill, and will not cause issues, however they must be killed before the Lich returns to the field. Blackout is usually a non-issue as well, unless (only an issue with lower level groups) the healer is the one affected. An instant heal ability can easily counter this problem, however.