Prioritize controlled first clears and avoid early river fights without lane priority to protect your tempo against Karthus's faster clear.
Focus on using your strong gank threat with (Q) to support lanes and force grouped fights where your (R) can shine.
This is a scaling, teamfight-focused matchup where you must survive early pressure and convert level 6 into objective control and lockdown opportunities.
Jungle Plan
Path to full clear safely first, then look to gank lanes with established crowd control and lane priority.
Contest Scuttle only if your lanes can move first and collapse quickly on Karthus to deny his tempo.
Use your (Q) and (R) to force grouped fights around dragon or Rift Herald, converting your crowd control into objective control and scaling denial.
Danger windows
Avoid isolated river fights before level 6 when Karthus can punish your low dueling power.
Be cautious of forced smite fights near objectives where Karthus's sustained damage and your low invade resistance put you at risk.
Respect Karthus's ability to full clear quickly and reach item spikes; avoid direct early invades without lane support.
Early game
Start with a full clear or three camps toward a lane ready to follow your (Q) for early ganks.
Use defensive wards on river entrances to spot Karthus's early invades and avoid low-health river fights.
Avoid contesting first Scuttle without nearby lane priority and prepare to counter-gank if Karthus attempts early pressure.
Power spikes
At level 6, your (R) enables strong area lockdown; use it to initiate fights and force objectives.
Karthus's level 6 global (R) demands you avoid extended low-health fights and be mindful of his presence across the map.
His first AP item spike increases his clear speed and damage; use this timing to cycle camps efficiently and contest objectives before he scales further.
Win conditions
Survive early jungle pressure by securing safe clears and using wards to avoid Karthus's invades.
Use your (Q) to gank lanes with priority and convert kills or summoner spells into dragon or Rift Herald control.
Force grouped fights post-level 6 where your (R) can lockdown multiple enemies, denying Karthus's damage output and enabling your team to secure objectives.
Tip: For Amumu vs Karthus, read overview, trading pattern, and danger windows first for a fast Jungle lane check.
