[REWORK] Karthus, the Deathsinger

I feel as though Karthus has a really dated kit and could use some love. Currently, you basically have to build either tanky ap and try to deal melee damage, or build pretty much full ap and rush in and die to take advance of his passive. Karthus doesn't really have the kit to support a bruiser ap role. He also has very little in means of protection against assassins.

My goal with this rework is to solidify Karthus as a close range teamfight mage, add flavor to his ultimate, and provide counterplay against assassins.

---------------Please look at the kit conceptually rather than nitpicking about numbers---------------

Passive: Song of Sorrow Dealing damage to an enemy marks them as defiled for 10 seconds reducing their magic resistance by 5/10/15 and enhancing Karthus's other abilities.

COOLDOWN: 300 seconds ACTIVE: When dead, Karthus can consume 2 stacks of Requiem to instantly respawn.

Q: Lay Waste RANGE: 875 COST: 20/26/32/38/44 Mana COOLDOWN: 1 second DAMAGE: 40/50/60/70/80 (+30% AP)

ACTIVE: Karthus detonates the target area after a 0.5-second delay, dealing magic damage to all nearby enemies. Defiled enemies take double the damage.

W: Grief RANGE: 900 COST: 90 mana COOLDOWN: 20/18/16/14/12 seconds

PASSIVE: Defiled enemies are slowed by 20%. PASSIVE: Karthus's armor and magic resistance are increased by 3/4/5/6/7 for each nearby defiled enemy. ACTIVE: Stun defiled enemies around you for 1.5 seconds.

E: Defile RANGE: 425 COST: 15/20/25/30/35 Mana per second COOLDOWN: 1 second DAMAGE: 30/40/50/60/70 (+30% AP) MANA RESTORED: 20 / 27 / 34 / 41 / 48 Mana

TOGGLE OFF: Karthus restores mana upon killing an enemy. TOGGLE ON: Karthus deals magic damage to all nearby enemies each second.

R: Requiem RANGE: Global COST: 150/200/250 COOLDOWN: 200/180/160 DAMAGE: 200/350/500 (+50% AP)

ACTIVE: Karthus channels for 3 seconds and, upon completing the channel, deals magic damage to all enemy champions. You can't move or deactivate after activating "Requiem" until channel ends or being interrupted.

PASSIVE: Killing an enemy champion with Requiem refunds its cost and grants a permanent stack. For each stack, Requiem does an additional 25 true damage.

Current Bonus: X