Use Jarvan IV's early game pressure and reliable (E)+(Q) engage to disrupt Karthus's full clears and deny his farming tempo.
Prioritize early river control and objective setups to leverage Jarvan IV's strong engage and objective control against Karthus's weaker invade resistance.
Jungle Plan
Invade Karthus during his first clears to force him off camps and deny his fast farming tempo.
Fight for river control and Scuttle Crab when lane priority allows, using (E)+(Q) to engage and trap Karthus.
Use early gank pressure to create lane leads, then convert numbers advantage into dragons, Rift Herald, and deep vision to restrict Karthus's map access.
Danger windows
Avoid invading or contesting camps when (E)+(Q) is on cooldown, as Jarvan IV's engage and escape options are limited.
Be cautious of isolated river fights if nearby lanes lack priority, as Karthus can punish with sustained damage and (R).
Respect Karthus's level 6 global presence; avoid extended low-health fights across the map where (R) can finish kills.
Early game
Start with a three-camp clear that leads to early gank opportunities on overextended lanes to force Karthus off camps.
Contest first Scuttle Crab only when nearby lanes have priority to avoid risky isolated fights against Karthus.
Avoid full clears that delay early pressure; use early ganks to snowball lanes and secure first dragon or Herald.
Power spikes
Level 2-3: Use (E)+(Q) to gank overextended lanes and force early summoner spells, disrupting Karthus's clear rhythm.
Level 6: Use (R) to trap Karthus or secure objective fights, locking him out of smite range and enabling kills or objective control.
First tank or fighter item: Use frontline durability to initiate fights and protect carries from Karthus's global damage.
Win conditions
Use early gank pressure with (E)+(Q) to snowball lanes and deny Karthus free farm and tempo.
Control river vision and secure early dragons and Rift Herald using Jarvan IV's strong objective engage and frontline presence.
Trap Karthus with (R) during objective fights or counter-jungling to deny his smite and force favorable skirmishes for your team.
Tip: For Jarvan IV vs Karthus, read overview, trading pattern, and danger windows first for a fast Jungle lane check.
