Reaper by MedievalDeath

Level 1
(D) - Quest: Health globes dropped from mercenary camps and enemy minions increase your mana regeneration. Reward: After gathering 20 health globes, Soul Globes dropped from Heroes also restore mana.
(Q) - Increases movement speed bonus of Wraith Form.
(W) - Every third basic attack deals more damage and restores mana.

Level 4
(Q) - Allows to deactivate Wraith Form, increases duration slightly.
(E) - Increases basic attack speed for a short period, once the channeling is done.
(W) - Quest: Deal an x amount (a lot) of basic attacks that deal more than y% damage (AKA up close) in one life. Stacks are lost upon death. Reward: Basic attack damage is increased permanently.
(E) - Deals medium damage over time to enemies near Reaper, for a short period, once the channeling is done.

Level 7
(D) - Collecting a Soul Globe increases basic attack damage significantly for a short period.
(Q) - Wraith Form heals Reaper over time up to a total of 13%.
(W) - Damage dealt from basic attacks to non-Heroes is increased greatly.
(Q) - Grants a significant movement speed increase for a short duration after Wraith Form.

Level 10
Death Blossom
Purgatory

Level 13
(W) - Activate to cause basic attacks deal maximum available % damage for 5 seconds.
(E) - Mana cost of Shadow Step is refunded if Reaper attacks an enemy Hero 2.5 seconds after using the ability.
(Q) - Wraith Form leaves a trail behind Reaper, slowing enemies greatly and blinding them for a short duration.

Level 16
(W) - Gain stacks that increase basic ttack damage the longer Reaper doesn't use his abilities. 10 stacks max. Stacks are lost upon using an ability.
Secondary Ability - Passive: using abilities grants ability damage reduction by 80% for 0.5 seconds.
(Q) - Can basic attack enemies during Wraith Form's duration

Level 20
(D) - Increases healing received from Soul Globes from 20% to 35%
(E) - Decreases channel time and mana cost slightly, grants two more stacks (three total), but decreases range greatly.
Death Blossom - Number of intervals increased from 3 to 5, movement speed reduction is lowered.
Purgatory - Slows enemies, basic attacks heal during the duration.

Skin ideas:
Buccaneer Reaper

The ghost pirate Blackheart saw the potential in the landlubber Gabriel Reyes and recruited him into his crew. Now known as the Reaper, the deadly marauder sails across the realms of the Nexus, serving Blackheart as his personal debt collector.