Evolve a swinub into Piloswine. At that point, you'll need to obtain a heart scale from the newspaper people or the underground, and then give it to the move maniac in return for teaching it ancient power. Then level up the piloswine (that knows ancient power) and it will evolve into Mamoswine. Just remember, your swinub wont be able to learn ancient power from the move maniac, but the piloswine will