Talk:Karthus/@comment-5077844-20140802100616/@comment-12314620-20140802102921

In theory Seraphs is great on Karthus.

The problem I have with Roa+Seraphs is that I feel that it takes too long to become impactful since building catalyst and tear means you are using 1900 gold to items with no offensive stats and both RoA + Seraphs take time to reach the state where they are actually powerful (10 minute wait for RoA, stacking the tear). RoA and Seraphs work extremely well on Ryze, since he scales with mana and has immediate power increase when he buys either of the items or even their components and therefore gets immediate return to the gold he spends. With Karthus the delay in damage that having Tear in your build creates makes every ultimate you cast before finishing seraphs ~700 gold weaker. Also I don't feel Karthus is that mana hungry that he needs both Roa and Seraphs. RoA and Seraphs reward Karthus like many other champions with what's likely his most powerful realistic lategame power. My own opinion is however that it's usually more risky build to go in soloQ environment than rushing something like Deathcap after RoA, since you can't really avoid fighting when you lack offensive power and are therefore more reliant on your team to carry you through your weak phase.

About replacing Seraphs Abyssals is an option, however I feel it only works on Karthus very late in the game when all the engages are teamfights, since the aura won't do anything if you use your ultimate to finish someone half way across the map. Other possible options include defensive item such as Banshees Veil (help against getting caught) and Guardian Angel (easier to position yourself for a good passive). Some other options I've found quite useful include WoTa, Liandrys and Twin Shadows for increased utility.

Note that these are only my personal opinions coming from plat level support main who likes to play Karthus in normals and in rankeds when support gets picked before me.