Not Updated For Current Season
The masteries shown here are not yet updated for the current season, the guide author needs to set up the new masteries. As such, they will be different than the masteries you see in-game.
Some people may decide to sell their boots at the very end and buy 4 arcangels, giving you about 200+ more AP.
Don't bother getting mejai's, because you will die lots. Not that it's good, just focus on finishing your build and you can solo a base despite your bad team.
If you know for sure that you're going to die, try to position yourself in the best place (preferably in the middle of a team fight) and spam all your abilities like crazy, you will almost certainly get a kill or 5.
Use lay waste to farm lots, it's pretty much free with your defile's passive (mana restore on kill) and clarity.
I chose clarity because even though you have this passive, it doesn't work while defile is active and you will almost certainly run out of mana at least three times while laning. A karthus with clarity is extremely annoying (endless harassment) which stops your enemy from farming.
Pros / Cons
- You will kill towers in 2-3 hits late game.
- You will also kill champions in 2-3 seconds.
- You will be easily killed by a melee dps (jax or yi especially).
- People call you cheap when you own them with your ulti.