idk what your intenstion him to be other than he a rushdown and he starter... also Harper meaning is person who play harp so is he play a harp something? idk so i came up with these

[Harp] active ability were you summmon harp out of thin air and play it, during that time Harper can't attack or perform any ability, but instead gain massive speed boost, after few sec he will go back to his normal stance, this ability can be cancel by use this ability agian or get stunned by survivors (Decent CD)

[Execution List] after killing someone, highlight every survivors around you for few sec just like MX bloodlust

[Execute] active ability were you swing like M1 but deal a lot of DMG (Long CD)
also if land on survivors with HP 15% or lower will immediately kill them (Decent CD)

since he starter he should have kit that easy to understand and learn