Passive: Iron Man
Whenever an enemy is damaged by one of Mordekaiser's abilities he generates a shield amount equal to 30% of the cost of the ability, reduced to 10% against minions. The shield's maximum amount is equal to 25% of Mordekaiser's maximum health. After a three second delay, Mordekaiser's shield decays at a rate of 2% of Mordekaiser's maximum health per second.
Q: Mace of Spades
5% Max Health
Passive: Mordekaiser's basic attacks deal 10/20/30/40/50 +(1% per 25 AD)(1% per 50 AP) of Mordekaiser's max health as bonus magic damage. This bonus damage contributes to Mordekaiser's Iron Man shield.
Active: Mordekaiser's next three basic attacks become empowered, doubling the passive bonus damage and converting his basic attack's damage to magic damage. For the first two Mordekaiser swings his runic mace in an arc, dealing damage to all enemies struck. For the third strike Mordekaiser swings his mace down, tripling the passive bonus damage and damaging all enemies in the area. Mace of Spades applies both on-hit and on-spell effects.
W: Harvester of Sorrow
10% Max Health
Mordekaiser generates an aura around the target, linking them to him for 4 seconds. After 2 seconds, Mordekaiser can recast the ability to end it prematurely.
Enemy Cast: Enemies near the targeted enemy are also damaged for 20/25/30/35/40% of the damage dealt to the targeted enemy. The damage dealt to the target and nearby enemies is stored as Agony. After 4 seconds or recasting the ability, Mordekaiser steals health from the target equal to the amount of Agony stored.
Ally Cast: Mordekaiser and the target ally gain 75 movement speed while moving in the other's direction. 20/25/30/35/40% of the damage dealt by Mordekaiser and the target ally is stored as Agony. After 4 seconds or recasting the ability, Mordekaiser and his ally are each healed for 50% of the Agony stored.
E: Siphon of Destruction
1% Max Health per Second
Mordekaiser generates a cone of spectral absorption that deals 10/30/50/70/90 (+.35 AP) magic damage per second. Enemies under the effect of Harvester of Sorrow have 10/20/30/40/50% of their movement speed stolen by Mordekaiser over 3 seconds and contribute Siphon of Destruction's full health cost to Iron Man. Mordekaiser retains the stolen movement speed for 3 seconds after either Harvester of Sorrow's or Siphon of Destruction's effects have ended. While Siphon of Destruction is active, Mordekaiser cannot attack or cast other spells.
R: Children of the Grave
Passive- Dragon Force: If Mordekaiser contributes to the takedown of the Dragon, Mordekaiser enslaves its spirit for 10 seconds. Dragon Force will kill Mordekaiser's current ghost and disable Children of the Grave's current effects, and casting Children of the Grave will kill the Dragon.
Active: Mordekaiser curses the target enemy, stealing 5/6.5/7% (+1% per 50 AP) of the target's health as magic damage before dealing 15/19.5/21% (+1% per 16.67 AP) damage over 10 seconds. Cursed enemies are afflicted with the same aura as Harvester of Sorrow, healing Mordekaiser for any damage inflicted by its effects.
I'll admit, I didn't even TRY renaming or completely redoing any abilities, partly because I don't know jack shit about metal music outside of Pentakill and "Indestructible" by Disturbed. I mainly just went with trying to make what he's got already healthier while retaining an appropriately thematic feel.