Character name: Luna
Ability: Drain a life away from someone when you kill them, but lose it when you walk on sacred ground*.
Details: You could either automatically get a buffer for when you get hit once you kill someone, or you could fire a debuffed (slowed, prevented from being diagonal) shot every once in a while that will steal their life if it hits them. Clearly, either of these are powerful enough to warrant a balance. Something that hinders them from sneaking up on/away from other players would be in order for a character of this type. Therefore... You would have to avoid certain areas if you want to keep your life. An offensive style is limiting.
*Sacred ground could be a variety of things.
Character name: Al
Ability: When holding ability, characters and bullets near you are heavily slowed. (Note: It would be interesting for proteus' drone to get slowed too, but that might get weird)
Details: Most of the ambiguousness comes from the arrangement of the circle.
1) Simple: a radius of 4-5 blocks that slows bullets and characters by 1.
2) Precise: a radius of 2-3 blocks that slows bullets and characters by 2.
3) Inner: a radius of 1-2 blocks that slows 2, and outside that, an outer ring with an added radius of 2 that slows 1.
4) Outer: a radius of 1-2 blocks that slows 1, and outside that, an outer ring with an added radius of 2 that slows 2.
Basically, it can be used defensively to dodge bullets, or offensively to trap them or throw them off. However, the slowed bullets will be a sure sign that he is in the nearby vicinity, so you don't want to give yourself away. Note that when characters/bullets leave the circle they should return to normal speed. This is where 3 and 4 are weird.
Lore: Al, short for Alcubierre, was more interested in improving the technology than improving his skills. It was revolutionary! But not good enough. He thought farther than bending light: what if you could bend spacetime itself? Eventually, he perfected his new kind of invisibility. Except it sucked because everything would get stuck in and on it, so everyone could see where he was. The revised version just uses the normal Invisigun technology, but can slow the nearby environment. (relative to yourself, of course.)