'Ello there, I kinda came in to this expecting to find a lore about some mysterious twin brother of Ryze (Raze, Ryze, get it? No? I'm terrible at jokes anyways). Anywho, I must say his kit seems rather... linear? Assassins tend to be a more of a high skill high reward kind of play style (or at least, that's what I think it is supposed to be like) rather than having a kit that's just clear cut. Additionally, I'd recommend having some way for him to get OUT of a fight. Right now, he just seems to be more of a dive fighter, which may actually be what you're looking for. However, if you wish to advance the assassin aspect of him, I'd recommend looking for some way that enables for him to get in, kill his target, and get out.
His E seems to be his only sense of mobility, which is perfectly fine, but I have to wonder if it's a point and click like Vi ult, or is it a dash like Warwick ult? His ult doesn't seem to really fit into his kit.
His kit seems to really focus on hurting (a lot) at close range, but his ult just kinda throws them back. It seems like if he would wish to test his skills on the rift, he'd much rather fight everyone in his way rather than just getting them out of his way.
I'm going to be skipping around to his W. Let me tell you, that is some CRAZY attack speed bonus. I mean, I'd just take him and get
or something like that (Please mind that I do not play AD champions so this build is probably not something you actually want to use). While it's true there is no other thing significant about his W, I feel like reducing the attack speed bonus and giving it some other ability would help.
Also, he has no passive. The passive is something that can really make or break a kit, so I would recommend adding one that can fit along with his lore. Speaking of which, his lore is a bit... generic. I would recommend really building a story behind it, and make it really flourish into something that can be differentiated from the rest of the champions and other characters in the game. Please remember in the case of lore making that it does not actually have to include some way in which they join the League. Don't forget a title too, it's always fun to have some sort of cool title for a champion to go along with their name. ^.^
That's about all I have that I could say, good luck on your champion. :D