Hello! My name is JuvX I am a Season 9 Grandmasters and a Season 10 Masters Jungle Main. I have previously mained Lee Sin, Nidalee, Evelynn and now I am currently playing Karthus due to his high skill cap and overall fun. Before I start this guide I just want to be real with you, are you ready to completely annihilate the rift with Karthus? If so, you came to the right place. Glory to the Reaper. :)

Lay Waste

Karthus briefly reveals the target area which he detonates after a 0.5-second delay, dealing 45 / 65 / 85 / 105 / 125 (+35% of ability power) magic damage to all enemies within, doubled when hitting only one target.
Lay Waste's damage is reduced by 15% against monsters.
During Death Defied, Lay Waste will cast at maximum range if cast beyond that.

Wall of Pain

Karthus creates a 800 / 900 / 1000 / 1100 / 1200 distance wide wall at the target location for 5 seconds. The wall reduces the magic resistance of enemies who pass through it by 15% for 5 seconds and applies a 40 / 50 / 60 / 70 / 80% slow which drops to half effectiveness after 1 second and then decays over the remaining debuff duration.

Defile

Passive: Karthus restores 20 / 27 / 34 / 41 / 48 mana whenever he kills an enemy.
Toggle: Drains 30 / 42 / 54 / 66 / 78 Mana every second. Deals 7.5 / 12.5 / 17.5 / 22.5 / 27.5 (+5% of ability power) magic damage every 0.25 seconds to all nearby enemies. Deactivating Defile deals 1 tick's worth of damage.

Requiem

After channeling for 3 seconds, Karthus deals 200 / 350 / 500 (+75% of ability power) magic damage to all enemy champions (regardless of distance).