Champ Idea - Scythe

So I just kind of thought of a new champion idea. The champion is a mid lane or jungle AD assassin. I didn't think too hard about a name, so here's a temporary one: Scythe.

Passive - Every champion kill you get expands your base vision by 10 units. (please tell me a balanced number, or if this is a terrible broken/useless passive) [cap is +100 units]

Q - Spins in a circle and slashes all enemies for physical damage

W - Marks a target. Scythe's next basic attack or ability will do bonus magic damage.

E - Throws a blade at a target that does physical damage. If Scythe manages to land 2 consecutive basic attacks within 2.5 seconds, the target is stunned for 1 second.

R - Scythe becomes invisible for 5 seconds. The next basic attack or ability will apply grievous wounds to the enemy and is a guaranteed critical strike.

I don't know enough about other League's champions' lores so I'm not qualified to invent a lore. If you have any ideas feel free to put them below.

(also im new to the forums so don't bash me for doing something wrong ;o)

Lore Concept:

Scythe grew up as a trained assassin in Noxus. He was taught that emotions were the cause of downfall. That anything other than the thrill of killing was useless and forbidden. And so Scythe followed. Throughout the Noxian wars, Scythe mercilessly slaughtered men, women, and children. He received recognition from Swain, and though he appreciated it, he never felt like he deserved it. There was something within Scythe that left a searing pain in his heart.

That searing pain came from a secret that Scythe bore.

It was the photographic memory of every single person he murdered. He could painfully remember each and every detail of his rampages. From the methods of killing to the sound of screams, Scythe remembered it all. That was his only nightmare, the only thing that kept him up at night.

They say that war is unforgiving. They say that war leaves you torn.

Scythe remembers everything.

He cannot forget.