Yes my apologies, I meant to close it up again, but forgot :)
Anyways for now its being closed down till I finish editing it, thanks for the feedback!

One can't provide feedback aside from what is shown, feel free to see the new guides submitted daily to understand why we can believe that any of them is - according to the owner's mind - finished and ready to be followed.

I'm still in the process of making the guide, I only opened it to show some people and gain some feedback. I literally only spent a few hours on it. So yes it needs fine tuning, thank you for your feedback, and the spell choices were explained.

How is the build good?

RoA is usually the first core item for actually holding on tfs, Elisa's is a troll pick to reduce CDR on troll summoner's.

You have 0 survivability, if focused in TFs you might die even before you can activate Zhonya. As Linear said, Karthus is not a suicide machine, it's actually good if you can hold on teamfights. You say karth is about his passive and you'll clearly need it A LOT for that build. You say he's not about his ult yet you have Revive.

I for once consider suicidal Karthus to be really effective, dying indeed but being able to easily take down at least two enemies with him. Your build is good, and your math is impressive, so I'm upvoting.

Another friendly tip: activate "Forced comments" to prevent trolls and suchlikes to downvote systematically.

You gotta know one thing if you're going to play Karthus.

You're not a suicidal machine, if you do that, you'll get reported for intentional feeding.

Your build is good, but your summoner spells and runes are stupid.

I suggest you change a few things about your guide.

I don't feel like you chose the right summoner spells, also, your guide doesn't explain enough about karthus, especially items, you should explain why you chose each item, because some people might not understand why you chose such and such item.