The skill evasion do the following:
Reduces the damage taken from area effect abilities by 1/2/3%
Does it reduce the damage from Karthus's Requiem ?
Requiem (Active): After channeling for 3 seconds, Karthus deals magic damage to all enemy champions regardless of the distance.
In the Wiki there is no example for Requiem.
There exist a various amount of AoE champion abilities, summoner spells, and effect-granting items in the game and they can all be put in the following categories: