Grave Keeper by Slombeeper

Level 1:

-Curse of the Undead: Quest: Hit 30 enemy heroes with Cursed Skulls. Reward: Cursed Skulls's cooldown is reduced by 1 second and deals 90 additional damage.
-Dark Dealer: Undead Pact costs 1 less skull and its cooldown is reduced by 2 seconds but lasts for 1 less second.
-Death Shiver: Reap stuns for 0.5 additional seconds.
-Benefitial Agreement: Undead Pact can now be used on allied heroes. Quest: Absorb 800 damage with Undead Pact used on an ally. Reward: Undead Pact lasts until the target runs out of range and 25% of the damage you take is dealt to the target, when used on allied heroes.

Level 4:

-Soul Harvest: Basic attacks against enemies heal for 30% of the damage dealt.
-Hard Cranium: Using Cursed Skulls grants 25 armor for 1.5 seconds, reducing all damage taken by 25%.
-Sacrifacal Pact: Quest: Kill 3 enemy heroes under the effect of Undead Pact. Reward: If an enemy hero dies while under the effect of Undead Pact, restore 50% of your maximum health.

Level 7:

-Cursed Corpse: Allies revived by Necromancy deal 32 damage per second around them. Deals 100% more damage to heroes.
-No Skin But Bones: Allies revived by Necromancy have 30% less health but the cooldown of Necromancy is reduced by 10 seconds.
-Remorseless Will: Allies revived by Necromancy move at 25% slower speed but deal 20% more damage.

Level 10:

-Bone Golem: Control a powerful Golem with new abilities.
-Graveyard: Cast Necromancy on all heroes that die within an area. Become unkillable.

Level 13:

-Hunger for Flesh: Cursed Skulls cost 1 less skulls and its cast range is increased by 20%.
-Decapitate: Killing an enemy hero with Reap grants 5 additional skulls and 15% movement speed for 3 seconds.
-Burried Alive: Hitting an enemy hero with all 3 basic abilities within 2 seconds puts them in statis for 2 seconds and restores 1 skull.
-Ancient Blood: Casting Undead Pact grants a free cast within 2 seconds to cast on a different target. The reduction of damage against you does not stack.

Level 16:

-Haunting Prescence: Grave Keeper deals 23 damage per second around him, slowing enemies movement speed by 15% for 2 seconds.
-Eternal Death: Killing an enemy hero with Reap increases their respawn timer by 20%.
-Bone Rattler: When a nearby enemy minion dies, the cooldown of Cursed Skulls is reduced by 0.75 seconds.

Level 20:

-Grave Golem: If the Bone Golem survives until its duration is over, Grave Keeper restores 50% of the skulls spent to summon the Golem and the current cooldown of Bone Golem is reduced by 25%.
-Graveyard Keeper: Graveyard also affects targets that has already died in the area and its radius is increased by 30%.
-Dead Land: When any hero dies anywhere, they instantly give the Grave Keeper 10 skulls instead of needing to be picked up. Additionally, Necromancy's cast range is increased by 125%.
-Undead Reaper: Basic attacks slow the target by 20% for 1.5 seconds and reduce the cooldown of Reap by 1 second.