Karthus Rework

Passive - Death's Embrace: When Karthus dies, he stays alive for around 10 seconds, automatically casts a weaker version of his ult (needs a much lower percent health threshhold), and is surrounded by Death's Gates, anyone between him and the walls will be targeted automatically by Lay Waste

Q - Lay Waste: Kathus targets a small circle on the ground and does damage there after 1 second, applying a slow, this has a short enough cooldown so that you can keep an enemy continually slowed.

W - Death's Gate: Karthus erects a wall that becomes active after 1 second, it knocks back any enemy that dashes into it towards Karthus, if Karthus passes through this he gains bonus movement speed.

E - Death's Chorus: Passive - Karthus has a constant circle around him that deals percent health magic damage. Whenever Karthus lands Lay Waste on an enemy champion, this damage is heavily increased for a few seconds. Active - when activated, Karthus gains increased Armor, Magic Resist, and Tenacity for a few seconds, taking damage increases the time this is active.

R - Requiem: Karthus stands still and channels for a few seconds, afterwards, any enemy below a certain percent of health is automatically killed, all other enemies take no damage.

Edit: Okay to give context to this rework. Karthus has been somewhat weak for quite a long time, his weaknesses far outweight his strengths, he's slow, squishy, and needs consistently great aim to kill an enemy. His Q and E both want to be leveled first so you have to choose between mana sustain and low damage, or high damage but running out of mana incredibly quickly. His kit revolves around him being in the middle of a fight but he's not nearly tanky enough for it even with the roa-liandary's-scepter-abyssal combo. This is focused around keeping his main playstyle, by making it feel much more powerful. His death's Chorus is intended to be his main farming tool now, but it will be relatively weak at first and to keep it's farming useful, you must land your Q consistently. Along with this, his fighting ability is now entirely based around his sort of "death lawnmower" status of running down an enemy using your E. Playing against Karthus will be poking him down as without casting his E, he will still be relatively squishy and have trouble aiming his Q if you stay on your toes. Along with this he's still relatively bad at fighting multiple people. As for the ult, this is intended to make it so it's current role is emphasized where it's to execute that one enemy who got away. Spellshields, invincibility, or just healing in general will be able to negate it so there is counterplay.