League Classic matchup
Karthus vs Kassadin
The lane, from both sides
Karthus’s side
- Weak against Kassadinfrom the AP Burst Mage build (Jungle)
RiftwalkRiftwalkRActive: Kassadin blinks toward the target location, dealing magic damage to all nearby enemies upon arrival. He then gains a stack of Riftwalk for 8 seconds, refreshing on subsequent casts and stacking up to 10 times. Riftwalk: For each stack, Riftwalk deals 60 bonus magic damage at an increased 100 mana cost. crosses 
Wall of PainWall of PainWActive: Karthus erects a wall of pain at the target location perpendicular to his facing that lasts 5 seconds, granting sight around its pillars and center. Enemies that touch the wall are inflicted with magic penetration and become slowed for 5 seconds, decaying over the duration. This can affect enemies only once per cast., which slows and nothing else, and 
Null SphereNull SphereQActive: Kassadin fires an orb of void energy at the target enemy that deals magic damage and silences them.'s silence stops 
RequiemRequiemRActive: Karthus channels for 3 seconds, then deals magic damage to all targetable enemy champions upon completion. mid-cast, including the one 
Death DefiedDeath DefiedPassiveInnate: Upon taking fatal damage, Karthus enters a zombie state for 7 seconds, during which he can cast his abilities at no cost. If Defile has been learned, it will remain toggled on for Death Defied's entire duration. Requiem becomes disabled after 4 seconds of the duration have elapsed. While under this state, Karthus becomes untargetable and immune to crowd control as well as prevents all incoming damage, but is also rendered unable to move, declare basic attacks, use summoner spells, and activate items. was meant to guarantee.
Kassadin’s side
- Strong against Karthusfrom the AP Assassin build (Mid)
Karthus cannot escape Kassadin's burst combo, and once Kassadin scales with items he can one-shot squishy immobile mages; hard CC and magic resist are the only real counterplay.
The lane in detail
KarthusKassadinKassadin-favored from the first Riftwalk on
A wall that slows 80% is still a wall a blink ignores.
RiftwalkRiftwalkRActive: Kassadin blinks toward the target location, dealing magic damage to all nearby enemies upon arrival. He then gains a stack of Riftwalk for 8 seconds, refreshing on subsequent casts and stacking up to 10 times. Riftwalk: For each stack, Riftwalk deals 60 bonus magic damage at an increased 100 mana cost. lets Kassadin bypass Wall of PainWall of PainWActive: Karthus erects a wall of pain at the target location perpendicular to his facing that lasts 5 seconds, granting sight around its pillars and center. Enemies that touch the wall are inflicted with magic penetration and become slowed for 5 seconds, decaying over the duration. This can affect enemies only once per cast.. Null SphereNull SphereQActive: Kassadin fires an orb of void energy at the target enemy that deals magic damage and silences them. can interrupt RequiemRequiemRActive: Karthus channels for 3 seconds, then deals magic damage to all targetable enemy champions upon completion. while Karthus is alive, but Death DefiedDeath DefiedPassiveInnate: Upon taking fatal damage, Karthus enters a zombie state for 7 seconds, during which he can cast his abilities at no cost. If Defile has been learned, it will remain toggled on for Death Defied's entire duration. Requiem becomes disabled after 4 seconds of the duration have elapsed. While under this state, Karthus becomes untargetable and immune to crowd control as well as prevents all incoming damage, but is also rendered unable to move, declare basic attacks, use summoner spells, and activate items. makes him untargetable and immune to crowd control after death.
Who has the lane, level by level
1–511–18- 1–5Karthus: Lay Waste at 875 against a 125 melee
- 6–10Even: Riftwalk arrives and the wall stops mattering
- 11–18Kassadin: A blink every 6 seconds, silence at 2
- 2Wall of PainLevel 2: 800 units of wall, a 40% slow, and 18 seconds until the next
- 6RiftwalkLevel 6: One blink of 700 units, and 60 more damage waiting on the next
- 9Lay WasteLevel 9: 120 a cast now, and 240 when it catches nobody else
- 9Null SphereLevel 9: The silence tops out at 2 seconds, against a 3 second channel
- 11RiftwalkLevel 11: Rank 2 cuts it to 6 seconds, and stacks hold for 8
- 13Wall of PainLevel 13: The maxed wall spans 1200 units and applies an 80% decaying slow
The numbers, head to head
KarthusKassadinAttack range, units
125
Nether BladeNether BladeWPassive: Kassadin's basic attacks restore mana each hit. If the target is an enemy champion, the mana restored is tripled. Active: Kassadin empowers his basic attacks on-hit for 5 seconds to deal bonus magic damage. only refunds mana inside that 125, and only on a hit that lands.
Maxed poke spells and their recovery
The silence blocks casting for 2 seconds; Karthus can resume 
Lay WasteLay WasteQActive: Karthus conjures a blast at the target location that detonates after 0.5 seconds, granting sight of the area and dealing magic damage to all enemies within, doubled when only one target is struck. while Null SphereNull SphereQActive: Kassadin fires an orb of void energy at the target enemy that deals magic damage and silences them. recovers.
Crowd control per cast, rank 1
One slows a champion who blinks. The other stops the cast that was the plan.
Magic resist at level 1, and who cares
31.25
Void StoneVoid StonePassiveInnate: Kassadin gains bonus attack speed equal to 15% of magic damage taken. reads 15% of the magic damage Karthus deals as Kassadin's attack speed.
Biggest number each, level 16 and 13
RequiemRequiemRActive: Karthus channels for 3 seconds, then deals magic damage to all targetable enemy champions upon completion. arrives from anywhere. 
Force PulseForce PulseEPassive: Each time Kassadin or a nearby champion casts an ability, Force Pulse gains a charge, up to 6 charges. At 6 charges, Kassadin can activate Force Pulse. Active: Kassadin consumes all charges and emits a pulse of void energy in a cone in the target direction that deals magic damage to enemies hit and slows them for 3 seconds. wants 400 units, a cone and six charges.
One is 200 seconds, the other is 7
RiftwalkRiftwalkRActive: Kassadin blinks toward the target location, dealing magic damage to all nearby enemies upon arrival. He then gains a stack of Riftwalk for 8 seconds, refreshing on subsequent casts and stacking up to 10 times. Riftwalk: For each stack, Riftwalk deals 60 bonus magic damage at an increased 100 mana cost. is a movement button. RequiemRequiemRActive: Karthus channels for 3 seconds, then deals magic damage to all targetable enemy champions upon completion. is one cast and three seconds of standing still.
Reach, from above
Karthus
Kassadin
Rings are ranges in game units, both radars on one scale. Abilities wear their icon, the basic attack wears the champion’s own face; the dashed ring wearing the opponent’s face is their longest reach.
The item race
Karthus
400gThe mage-lane opener, taken over the mana start when the silence is the problem.
1200gEvery level-up hands back 150 health and 200 mana, which is what pays for standing in Defile.
2800gHealth and mana support Karthus through repeated trades while Rod of Ages accumulates its bonuses.
3260g2.5 seconds untargetable every 90, spent on the arrival and not on the poke.
Kassadin
700gRiftwalk adds 100 to its own price per stack, so the pool has to grow faster than the ultimate does.
1100gAimed at 30 base magic resist, and at a champion who has to stand still to finish Requiem.
3300gRiftwalk scales at 70%, and Magical Opus multiplies whatever the rest of the build bought.
2700gThe stack cost is the problem, and 1000 mana is the answer that also reads as ability power.
Play it as Karthus
- 1Farm from 875 and never from 550:
DefileDefileEPassive: Karthus restores mana whenever he kills an enemy. This passive is disabled when Defile is toggled on. Toggle: Karthus surrounds himself in a necrotic aura that deals magic damage every second to all nearby enemies. Toggling Defile off triggers a final tick of damage. Defile is toggled off automatically if Karthus becomes unable to pay its mana cost.'s aura sits inside the 650 the silence is fired from. - 2Walk out of the fight before starting RequiemRequiemRActive: Karthus channels for 3 seconds, then deals magic damage to all targetable enemy champions upon completion.. It channels for 3 seconds, and Null SphereNull SphereQActive: Kassadin fires an orb of void energy at the target enemy that deals magic damage and silences them. reaches 650 units.
- 3Toggle DefileDefileEPassive: Karthus restores mana whenever he kills an enemy. This passive is disabled when Defile is toggled on. Toggle: Karthus surrounds himself in a necrotic aura that deals magic damage every second to all nearby enemies. Toggling Defile off triggers a final tick of damage. Defile is toggled off automatically if Karthus becomes unable to pay its mana cost. off the moment he blinks out of the 550. The aura keeps billing mana whether anything is inside it or not.
Play it as Kassadin
- 1Save Null SphereNull SphereQActive: Kassadin fires an orb of void energy at the target enemy that deals magic damage and silences them. for the RequiemRequiemRActive: Karthus channels for 3 seconds, then deals magic damage to all targetable enemy champions upon completion. channel once he is level 6; the wave can wait 9 seconds.
- 2Walk the wave for Nether BladeNether BladeWPassive: Kassadin's basic attacks restore mana each hit. If the target is an enemy champion, the mana restored is tripled. Active: Kassadin empowers his basic attacks on-hit for 5 seconds to deal bonus magic damage. mana: 8 back on a minion, 24 on a champion.
- 3Blink through Wall of PainWall of PainWActive: Karthus erects a wall of pain at the target location perpendicular to his facing that lasts 5 seconds, granting sight around its pillars and center. Enemies that touch the wall are inflicted with magic penetration and become slowed for 5 seconds, decaying over the duration. This can affect enemies only once per cast. rather than around it. A decaying slow does nothing to a 700 unit jump.
The catch
Null SphereNull SphereQActive: Kassadin fires an orb of void energy at the target enemy that deals magic damage and silences them. can interrupt RequiemRequiemRActive: Karthus channels for 3 seconds, then deals magic damage to all targetable enemy champions upon completion. before Karthus dies. During Death DefiedDeath DefiedPassiveInnate: Upon taking fatal damage, Karthus enters a zombie state for 7 seconds, during which he can cast his abilities at no cost. If Defile has been learned, it will remain toggled on for Death Defied's entire duration. Requiem becomes disabled after 4 seconds of the duration have elapsed. While under this state, Karthus becomes untargetable and immune to crowd control as well as prevents all incoming damage, but is also rendered unable to move, declare basic attacks, use summoner spells, and activate items. he is untargetable and immune to crowd control, so Kassadin cannot silence that channel. Karthus must still begin RequiemRequiemRActive: Karthus channels for 3 seconds, then deals magic damage to all targetable enemy champions upon completion. within the first 4 seconds of the passive, before it becomes disabled.
The kits at a glance
Karthus
Full abilities- Death Defied
- Lay Waste
- Wall of Pain
- Defile
- Requiem
Kassadin
Full abilities- Void Stone
- Null Sphere
- Nether Blade
- Force Pulse
- Riftwalk
Base stats, side by side
| Stat | Karthus | Kassadin |
|---|---|---|
| Health | 465 (+75) | 511 (+78) |
| HP regen | 1.21 (+0.11) | 1.49 (+0.1) |
| Mana | 331 (+61) | 275 (+45) |
| Attack damage | 45.45 (+3.25) | 56.2 (+3.9) |
| Armor | 18.5 (+3.5) | 21.2 (+3.2) |
| Magic resist | 30 | 31.25 (+1.25) |
| Attack speed | 0.625 (+2.11) | 0.64 (+3.7) |
| Move speed | 335 | 340 |
| Attack range | 450 | 125 |
Level-1 values with per-level growth in parentheses, read from the Classic client and re-checked against it on every update.
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