Talk:Karthus/@comment-212.117.1.33-20111020162232/@comment-569195-20111020235842

That's actually a really good question. There are times when died and tried to use my ult after a few q's and it didn't work but im pretty notorious for accidentally hitting the wrong key so I assumed i made a mistake. I just did a quick google search and found this forum post

During Death Defied there is a set window in which Karthus can actually use his ult while in Death Defied form, when this runs out Requiem turns grey and cannot be cast because he doesn't have enough time to channel the full spell as we all know.

Seems like that answers the question. Can anyone confirm?