Aurelion Sol 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

Deathfire Touch

Manaflow Band

Absolute Focus

Scorch

Precision

Presence of Mind

Cut Down

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

Keep your breath on one champion
Keep Breath of Light (Q) on the same champion: each second triggers a burst of bonus damage and gives you Stardust.
Farm your Stardust
Farm with Singularity (E): every enemy that dies inside, minions included, gives you Stardust, which permanently strengthens all your abilities.
Fly to escape or chase
Cast Astral Flight (W) to escape a gank or to chase: during the flight, Breath of Light (Q) has no cooldown and no channel limit.
Hit several champions with your R
Cast Falling Star (R) on several enemies: it stuns them, and each champion hit gives you Stardust to upgrade your next cast into The Skies Descend (R).

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