Thane, Shadow of Spite
Aesthetics would be similar to a male version of Vayne (long black coat, boots, generally dark/edgy and noble outfit) without the glasses. Similar to the protagonist in the new Assassin's Creed game. Here's a picture for reference.
Wields leather gloves equipped with long, metal claws protruding from each finger.
Passive: The Act of Darkening - Whenever Thane enters the view of the enemy team, he gains movement speed, flat armor penetration, and attack damage that scale up with his levels. This buff is consumed by wards, TF ult, and other vision granting abilities/items. This buff has a recharge time of 30 seconds. This buff lasts 5 seconds. The cooldown only begins once he leaves vision. As long as he is visible, the cooldown will not continue.
Q: Consternation - Fires wisps of shadow that connect to the first target hit, dealing magic damage and snaring them for 1/1.25/1.50./1.75/2 seconds. Thane can recast this ability, fading into shadow and becoming untargetable while dashing towards the target, but the moment he recasts the ability, the snare is removed. He becomes tangible again when he lands and gains 15/25/35/45/55 AD and 15/25/35/45/55 armor penetration, but only against the target. If Thane or an ally kills the target within 5 seconds of the initial skillshot landing, this spell's cooldown resets, costs no mana for a short time, and reactivates his Passive buff. Damage scales off of AP and spell's level.
W: Elohim Meth - Passive: Thane deals small amounts of true damage on each autoattack that increases for a short time whenever he hits an enemy champion. Autoattacks as well as each cast of The Parting provide brief movement speed boosts. Active: Significantly lowers Thane's attack speed, but significantly increases the damage of his autoattacks, and cleaves targets in an area in front of him and makes them bleed. Bleed damage scales with AD and spell's level. Movement speed boost scale off of spell's level. Extra autoattack damage scales with AD and spell's level.
E: The Parting - Thane spins through a target with his claws while dealing damage to them. 0.3 second cooldown. No mana cost, but consecutive casts on the same target uses more and more mana, but the more he spins through the same target, the more damage this ability deals. Scales off of AD and spell's level. The spin will always take Thane 50 units past the target, keeping him very close, but a timely sidestep in the opposite direction will heavily reduce his sticking power unless he has his Q or Ult up. 200 unit range. (Thane's basic attack range is 125)
Ult: Hatred of Desiderium - Thane instantly dashes to an enemy champion, dealing HEAVY physical damage and appearing behind them. Somewhat heavy mana cost. If this spell does not kill the enemy champion, it goes on an unalterable (can't be changed by CDR) 60 second cooldown. If it kills the enemy, this spell's cooldown resets, costs no mana, and reactivates Thane's passive buff. Damage scales with AD and spell's level. Medium-long range (think Talon's E.)