Build Guide by
Not Updated For Current Season
Note from the author:
The guide below is an insight into my general play style and how I handle situations as Karthus, any number of tweaks can be applied to this guide and i will attempt to do so as time permits.
brief Karthus abilities break down:
Lay Waste provides mana upon last hit via the passive from the Defile ability, but should be used sparingly and mainly for last hits to replenish mana until the time is right to attack the enemy champ, Karthus is mana hungry. Keep moving and going for last hits that may also damage your opponent while last hitting a minion and opportunities to hit just the enemy champ - for the double damage modifier.
With Karthus' auto attack being so weak, i use it to mask my Lay Waste casts to keep the enemy on his toes, his casting animation somewhat resembles his auto attack swing. Using Lay waste and Defile's active aoe on champs is a killer, apply Wall of Pain's debuff for maximum effect. I enjoy checking brush, attacking stealthers (Akali), harassing tower humpers, and leading runners with this ability.
Wall of Pain provides a powerful debuff your entire team can benefit from, It lowers Armor, Magic Resist, and Movement Speed. Wall is useful in escaping or cutting enemy champs off from a fleeing friendly champ. Flashing from the brush, then popping a wall behind your target can be deadly. I also use Wall defensively at towers to slow attackers for turret shots and buy time (Trynd). When i die wall is first priority, the debuff still helps the team, then Requiem isn't cast too far behind Wall.
Defile's passive allows to to lane much longer and the active deals massive damage in conjunction with Wall of Pain and/or Lay Waste spam. I wouldn't use it much until level six or an early kill attempt with a majority of your mana.
Requiem is a great ability for last hitting runners or softening up the enemy team when retreating from or dying during a team fight. With assists alone you can maintain high stacks of Mejah's Soulstealer, giving you the ap you need. Requiem is why Karthus always takes mid, his ultimate can assist anywhere on the map, allowing Karthus to hold a lane or push while helping out the team a little. Requiem is Karthus' claim to fame, making for an infamous reputation if used correctly.