I know there's already a necromancer-themed hero, but I think this one would be much more interesting, and I also don't see a problem with having two necromancer-themed characters since they have different abilities and playstyles.
I like the idea of Graves being a necromancer, but I didn't like how they developed his abilities. I'll share some ideas here that I think would be more interesting.
Ability 1:
Skill 2: The current skill remains.
Ability 3:
Skill 4: The current skill remains.
The slide isn't the only thing Viper has, and I don't see any problem with other heroes being able to slide like him either. And we only have about 2 items that increase slide distance, which are burst fire and fleetfoot.
Opening round costs 1600 and also increases by 40%, long range also increases by 40%, Intensifying Magazine increases by 45%, so slide mastery is at the same level.
This would be a very interesting item that could even change the way you play. I really like Vyper because I find sliding fun, but I hate the rest of the champion, which is awful. This would be a fun item that could bring Vyper's sliding mechanic to other heroes.