The next Community Day is Piloswine On February 16, 2019 from 2-5PM Eastern time. The exclusive move for this is Ancient Power if you evolve Mamoswine before 6PM.
Gyms and Raids
Here is a rank of all the moves for Feraligatr. Ancient Power is the worst move for it. Against bug and against ice it is the best move for Mamoswine. But if we look at all the best attackers against bug and against ice is no where near the top. Mamoswine with Ancient Power looks to be just a collectors item.
Trainer Battles
Since trainer battles have a completely different set of move stats, lets look at this seperately. Also, TDO is usually maximized for trainer battles instead of DO@20. Under Master League trainer battles, Ancient power looks to be the worst move. Even against bug and ice types, Ancient power is behind Stone Edge. No changes here either for Mamoswine.
Comments or Suggestions
If you have any comments or suggestions, please follow up on this subreddit post