Rough Champion idea

Hi, thank you for taking the time to look at this champion idea. This has been floating around in my head for a while now but I think I have enough to post about it. I've always loved Thresh's backstory and so this Champion concept is based off of that.

Neave - The Lost Prisoner "In times before the shadow isles you know now there was an order charged with the task of guarding corrupt and evil artifacts. When the black mist fell so did the order, leaving the treasures unguarded and they were angry. The hate they harbored for their malevolent warden erupted and filled the only living body ever kept in these dungeons. A warlock who enchanted his own flesh, his anger was like a magnet to these magical tools. His body struggling to contain all of this dark power burned and boiled, Screaming filled the now empty halls. To help preserve his form he put on a magic nullifying straight jacket, it would do him- no,** them** no good to die now. As they walked away from their once prison they laughed, nothing would stop the torrent about to befall upon their Torturer."

So enter Neave, An AP scaling champion. I'm not very good with numbers and balancing so I haven't added much of those but I imagine his abilities are like this. Also please feel free to tell me this is horribly broken or under powered as long as you also provide ways to fix it. I would love to hear some feedback!

Passive: Fueled Hatred; Whenever Neave is hit by a spell he gains hate stacks, once he reaches max his next ability fears. **Q: Hideous Screams; **Neave screams at a champion dealing damage and slows the target. (if at full Hate stacks it fears instead.) **W: Uncontrollable Magic; ** Neave's magic bursts giving him a spell shield for a small amount of time and slows him. If at full hate stacks he fears in a small area around him. (possibly instead of slowing him, but that might be too good.) E: Punishment; Passive - Every kill or assist feeds his permanently increases his fear length by a VERY small amount(This might be too good but I like the idea of a passive based on kills/assists) Active - Neave slashes in a cone, increasing in damage by the end of it. R: Forsaken Power; Neave burns away his bonds, showing his true form. On the initial cast he slows in an area around him (If full hate stacks he fears) It also takes a high percentage of his mana and gives him increased mana regen. (Potentially a whole bunch) He then deals increased damage based on missing mana for the duration.

If you have any questions or ideas please feel free to ask away. Thank you for reading!