Karthus mains
I use Cooldown blues on on Kaarthus would scaling or flat be better, they give the same amount once you hit level 10
I use Cooldown blues on on Kaarthus would scaling or flat be better, they give the same amount once you hit level 10
Flat cdr is always better if you are buying cdr items at all.
The only thing you'd need CDR for would be his ultimate, but even then getting them is a waste because pure AP would be better.
I honestly don't like CDR runes on him, I feel like MR is much better. Two of his core items already have some CDR on them (
) and really the only thing you'd want any CDR for would be his ult which, by late game, already has a low enough cooldown to be able to use after pretty much every team fight.
But yes, flat CDR is better.
CDR helps with other abilities too because his ult is meant to last hit, but he needs to spam his q to do damage before that.


https://gyazo.com/2006d2cca0138ec987368f135615ff67
Runes
AP Pen Marks HP Scaling Seals AP Scaling Glyphs
Either Movespeed Quints or AP Quints. Tbh MS Quints might be better as Karthus is slow and immobile.