The skill order is as follows: Q is always leveled first because it is the skill Karthus wants to use to push the minions and can be very strong in an all-in situation even at level 1. This is exactly why it is maximized first. If an opponent is isolated, Karthus’ Q – Devastate deals double damage.

Karthus’ E is “Annihilation”. When Karthus kills a unit, he regains mana. Activating the ability deals 0.25 seconds of magic damage to active enemies. You can switch the ability on and off whenever you want. Deactivating the ability also deals a tick of damage. As Lane Karthus, you mainly want to use the passive of the ability, as you want to work a lot with your Q’s.

In addition, Karthus’ W – Wall of Pain costs 70 mana, which corresponds to 2-3 Q’s depending on your level. This is another reason why Karthus is particularly strong as soon as you complete “Lost Chapter” and have fewer mana problems.

At level 3, put another point into the Q to significantly increase your damage. All In’s with Supporters that offer crowd control effects are ideal for Karthus on the Botlane.

A possible variation is to put a second point into Karthus’ E at level 3, simply to increase passive mana regeneration when killing minions. This is advantageous if you have used up a lot of mana in the first 2 levels, but cannot or do not want to aim for a recall yet.

In this case, you can postpone skilling the W to level 5. As a rule, however, your skill order will be Q->E->Q->W.

Then maximize your skills as normal in the following order: Q > E > W. You skill the ultimate as usual at level 6, 11 and 16.