Talk:Karthus/@comment-8506165-20140305190817/@comment-8506165-20140331090518

and serve you better for HP sustain though, unless you're staying in lane for multiple levels after getting Catalyst, in which case you can't be doing too badly - I mean, the XP gap between levels once you've gotten Catalyst isn't inconsiderable, so if you're staying in lane long enough for the Catalyst passive to give you more than you get from Flask + Belt (four levels total) then you obviously aren't recalling incredibly frequently. Unless you got Catalyst really early, in which case I'd say you're still not doing too badly if you're raising 1200 gold in time for the gap between levels to still be low. Not to mention Flask gives you on-demand sustain rather than potentially forcing you to stay in lane while low until your level-up.

If you recall even once before gaining 4 levels with Catalyst then your flask recharges too and your health is refilled, so it's another 4 levels you need for Catalyst to be the best "sustaining fragile laner" option. Granted, Catalyst gives more mana, but I've found that early on Karthus doesn't have tremendous mana problems once he has Tear if he's CSing well.