From PokéFarm Q Official Wiki
A special ring that allows a fully evolved Pokémon holding a Mega Stone to evolve even further. This evolution is only temporary though, and can wear off in time.
Before you can use Mega-Evolution on PFQ, you have to unlock the Mega Ring.
- In the official Pokémon X/Y games, the player can obtain a Mega Ring and use it to Mega-Evolve Pokémon during battle, provided that said Pokémon is holding its required Mega Stone.