Matchup

Sejuani
Sejuani
45%
55%

vs

49.3%

over 144 games

Karthus
Karthus
17%
83%
Heavy AP damageCountered by stasisSustained DPSHigh burst

Skill matchup

Build vs Karthus

Build adapted to this matchup

Starting items

Mosstomper Seedling
Health Potion

Core build

Sunfire Aegis
1vs AD
Kaenic Rookern
2vs AP
Jak'Sho, The Protean
3vs Hybride

Standard

Boots of Swiftness
4vs Slow
Heartsteel
5Survival

Summoner spells

41199%
6111%

Anti AD

Plated Steelcaps
4vs AD
Unending Despair
5vs AD
Randuin's Omen
vs AD
Frozen Heart
vs AD
Knight's Vow
vs AD
Dead Man's Plate
vs AD

Anti Heal

Thornmail
6vs Hybride

Anti AP

Mercury's Treads
4vs CC
Hollow Radiance
5vs AP
Force of Nature
vs AP
Spirit Visage
vs AP

DPS

Dusk and Dawn
Mage tank

Other options

Heartsteel
Survival
Protoplasm Harness
Survival
Zeke's Convergence
Tank
Warmog's Armor
Survival
Bandlepipes
vs Hybride
100.0% WR3 games
ResolveResolve
AftershockAftershock
Font of LifeFont of Life
ConditioningConditioning
OvergrowthOvergrowth
PrecisionPrecision
Legend: AlacrityLegend: Alacrity
TriumphTriumph
Attack SpeedHealth ScalingHealth Scaling

Power Spikes

Strength by game phase

Early (0-15)
Mid (15-30)
Late (30+)
SejuaniSejuani
KarthusKarthus
Neutral
Neutral
Neutral

Karthus's abilities

Passive, spells and ultimate

Death Defied (P)

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

Cooldowns

Cooldowns by spell rank

LevelQWER
30s15s0.5s
60s15s0.5s3m20
90s15s0.5s3m20
110s15s0.5s3m
160s15s0.5s2m40
180s15s0.5s2m40

Playing against Karthus

How to counter and exploit weaknesses

1

Zhonya's, Edge of Night, and Banshee's block/cancel his R — buy one of these items if Karthus focuses you.

2

His Q deals double damage on isolated targets: stay in your minions or near allies to split the damage.

3

Shields, Soraka R, and heals can counter his R if well-timed — save an emergency heal for Requiem.

4

Karthus is immobile and squishy — dive him quickly to eliminate him before he deals continuous damage.

Source: op.gg + LTL Engine · Patch 16.9.1 · May 9, 2026