Innate: 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.