Delete Scorch, it's just stupid...
Ok, so the rune "Scorch" from the power section from sorcery is just so bad. "Gathering storm" rune is in the same section as Scorch, So why would I pick Scorch instead of Gathering storm? Scorch would seem a perfect pick for Karthus, but at lvl 18 it gives only a bonus consisting of a bad 60 magic damage, while at lvl 18 "Gathering storm" gives me 84 ap, surpassing Scorch regarding damage. Needless to say that Scorch has a cooldown of 20 seconds and Gathering Storm would give me the bonus damage to all my abilities... Tell me if I'm wrong, I really dont get it...