Infectious, but a crewmate. When they press kill on someone, if that player is an impostor or neutral killing, they're notified that they've been proselyted, that players' kill button will no longer work, and they then have 'Proselyted' next to their name. That player is then a crewmate and wins with crew. They still have the ability of their original role. So that this role isn't to powerful, if they attempt to proselytise a crewmate, the Proselyter kills themself with the cause of death 'Misfire'. If the Proselyter proselytises an impostor, that impostor will be able to reveal their teammate, I guess.
Options:
Proselytise Cooldown.
Max Proselytises.
Proselyted Count Mode.
Can Convert Evil Neutrals.