Teron Gorefiend by GDouchington

Yellow for passives, Blue for actives, and Purple for Heroic abilities.

Level 1
 Block - Periodically reduces the damage received from Hero basic attacks by 50%. Stores up to 2 charges.
 Reveling in Death - Whenever a minion or mercenary, both ally and enemy, dies near you, you restore 0.5% of your maximum health.
 Death's Reach - Mortal Coil travels 50% farther, and refunds 20 mana if it hits a Hero.
 Piercing Darkness - Mortal Coil passes through non-heroic enemies, dealing its initial damage to them.
Level 4
 Dark Embrace - Mortal Coil's damage over time heals you for the same amount while you remain close to the victim.
 Remorseless Tendrils - Gorefiend's Grasp deals 150% more damage to minions and mercenaries and stuns them for 3 seconds instead.
 Obliteration - Basic Attacks deal 50% damage to enemies close to the primary target.
 Boon Blossom - You move 10% faster while under Doom Blossom's cloud, increasing by 5% every second you remain there.
Level 7
 Touch of Darkness - Activate to increase Basic Attack damage and speed by 20% for 6 seconds, each attack costs 10 mana. (30 second cooldown)
 Destructive Reach - Doom Blossom's cast range is increased by 40%.
 Death Pact - Activate to sacrifice a friendly lane minion and heal yourself for 20% of your maximum health. (60 second cooldown)
 Dying Grasp - Gorefiend's Grasp is cast automatically, for free, when you die. When used this way, it deals additional damage equal to 10% of the victims current health.

Level 10
 Full Circle - Resurrect yourself. Only usable within 5 seconds of dying.
 Death Strike - After a short delay, swing your weapon in a wide arc and gain a shield based on the damage dealt.
Level 13
 On a Pale Horse - You move 10% faster while mounted, and stuns, slows, and roots made against you are 50% shorter.
 Virulence - Basic Attacks against enemy Heroes deal bonus damage equal to 1.5% of their maximum health, and reduce their Basic Attack damage by equal to half that amount for 2 seconds.
 Unholy Power - Mortal Coil's damage over time effect lasts 1 second longer and deals its bonus damage regardless of distance.
 Spell Shield - Upon taking Ability Damage, reduce that damage and further ability damage by 50% for 3 seconds. Can only be triggered once every 30 seconds.
Level 16
 Armageddon - Doom Blossom's area of effect grows 10% larger every second.
 Ruin - Mortal Coil deals 100% increased damage, but its cooldown is also 100% longer.
 Unbreakable Armor - Activate to reduce all damage taken by 50%. Each time you take damage, the damage reduction is reduced by 10%. Lasts 6 seconds. (60 second cooldown)
 Endless Tendrils - Gorefiend's Grasp range is increased by 10% and it now grabs up to 5 enemies.
Level 20
 Deja Vu - When you resurrect with Full Circle, you instead have the health and mana you had 3 seconds prior to your death.
 Butchery - Death Strike now swings a second time, 0.5 seconds after the first swing.
 The Wheel Keeps On Turning - Whenever an enemy Hero you have recently damaged is killed, the cooldown of your Heroic Ability is reduced by 10 seconds.
 Nexus Blades - Basic Attacks deal 20% more damage and slow the target for 1 second.

While Gorefiend's default skin would be based on his appearances in The Burning Crusade, perhaps an alternate skin could be based off his Warcraft 2 appearance, with a yellow cloak and hood, as well as a plain wooden truncheon for a weapon.