Xerath vs Karthus

Not enough games

High burstHeavy pokeCountered by stasisHeavy AP damage

Build vs Karthus

The champion's reference build, for lack of enough games in this matchup

Starting items

—

x2—

Core build

1—

2—

3—

Standard

4Magic pen

5—

Summoner spells

100%

Anti CC

4vs CC

Other options

—

Sorcery

Arcane Comet

Manaflow Band

Transcendence

Scorch

Precision

Presence of Mind

Coup de Grace

Strength by game phase

Passive, spells and ultimate

Death Defied (P)

Upon dying, Karthus enters a spirit form that allows him to continue casting spells.

Cooldowns by spell rank

Level	Q	W	E	R
3	0s	15s	0.5s	–
6	0s	15s	0.5s	3m20
9	0s	15s	0.5s	3m20
11	0s	15s	0.5s	3m
16	0s	15s	0.5s	2m40
18	0s	15s	0.5s	2m40

Tips to maximize your impact

Charge Arcanopulse to poke from range
Charge Arcanopulse (Q) to poke from long range: its range grows with the charge, but you slow down by up to 50% in the meantime.
Slow before your Arcanopulse
Slow your target with Eye of Destruction (W) before Arcanopulse (Q): the center of the zone slows the most, and a slowed target dodges poorly.
Stun, then center your Eye
Land Shocking Orb (E), then center Eye of Destruction (W) on the target: stunned, they can't dodge it, and the center slows the most.
Finish from long range with your ult
Cast Rite of the Arcane (R) to finish a fleeing target or support a distant fight: your shots reach 5000 range, with bonus damage per champion hit.

How to counter and exploit weaknesses

Stay near your minions
Stay near your minions or your allies: Lay Waste (Q) deals much more damage when the blast hits only one enemy.
Jump on him if you can
If you can engage, jump on him: Karthus has no dash or leap to escape.
Don't stay low once he hits 6
Once he hits level 6, back instead of staying at low health: Requiem (R) hits every enemy champion wherever they are, 3 seconds after he starts channeling.
Save your protection for Requiem
If you have a shield, a heal or invulnerability, save it for Requiem (R): it hits every enemy champion 3 seconds after he starts channeling.
Move away after he dies
Once Karthus is dead, move away: Death Defied (passive) keeps him in spirit form for a while, and he can still cast his spells.

Patch 16.21.1