Karthus

Karthus turns sheer hunger for damage into a win condition more directly than almost anyone. Everything about his kit points to a single goal: keep hurting enemies regardless of what happens to him. Death Defied allows him to keep casting in spirit form once he has died, so an attacker who dives Karthus frequently ends up losing more health than the kill was worth, since he just stays in the fight and keeps pouring out destruction.

Lay Waste sits at the center of his rhythm. It is a delayed blast with a short cooldown that does extra damage to enemies standing alone. To play Karthus well, you have to keep landing these small explosions constantly, whether you are last-hitting, poking, or trading in duels, because one missed Q is wasted damage and his kit offers no burst combo to make up for it. Defile supports this in two ways: it passively returns mana on kills to feed his constant casting, and when activated it turns him into a moving damage aura for fights at close range. Wall of Pain strips magic resist and slows any enemy who crosses it, which sets up his damage and blocks escape routes.

The global threat

Requiem shapes how he is felt across the map. After a three-second channel, every enemy champion takes damage wherever they happen to be. Enemies at low health are never truly safe, and Karthus can influence fights far from his position. That constant pressure changes how opponents behave from the mid game onward.

He cannot move, has short range for a mage, and depends heavily on where he stands, so he is a risky bet in the late game. Players who enjoy a long war of attrition, careful discipline, and the mind games that come with a map-wide execute will likely find Karthus very rewarding to master.