Outsider that sounds like it should be a Townsfolk

Guardian (Outsider): On your first night, choose a player (not yourself): they can't die.

Since the Guardian is forced to pick someone the first day, they should have no clue which players would benefit the good team to be protected, and which ones would hurt the good team.

While it's a role that can be tested, and it could protect an information gathering role, it could also end up protecting people whose death would benefit the town, like evil players, characters that trigger on death in the night, and certain outsiders.

If town wants the protected player dead, they will first need to spend a day getting rid of the Guardian, before the protected player can be touched, hence why I'd consider the character an outsider.

Jinxes:

Pit-Hag + Guardian: If the Pit-Hag creates an evil Guardian, the Guardian's ability disables when there are less than 5 players alive

This jinx is exists for the same reason the SW ability stops working at 4 living players.

Roles this character would probably pair well with:

Assassin, Devil's Advocate, Pacifist, Damsel, and any role that wants to die in the night (Ravenkeeper, Sage, etc...)