Question: is ancient power mamoswine good?
Answer: Ancient Power. Let's be clear, Ancient Power is NOT Mamoswine's best Charge Move for PvE. It does not benefit from STAB (Mamoswine is not a rock type Pokémon), and it's not a really good Charge Move for gyms and raid battles. Furthermore, Mamoswine also has access to Stone Edge, a better rock type Charge Move for PvE.