Pokémon Sun and Moon, the latest releases in Nintendo’s hit monster-collecting series that came out for the 3DS last November, is finally giving Mewtwo’s Mega Evolutions.

Mewtwo is one of the franchises’ most popular and powerful characters, and his Mega Evolution forms make him even stronger. Sun and Moon are already big hits, selling over 14.69 games in 2016. This feature could keep those players engaged.

Mega Evolutions debuted as a feature in X and Y, the generation of Pokémon games that preceded Sun and Moon. It pushes a Pokémon to a stronger form that lasts through a battle (normal evolutions are permanent). The feature was downplayed in Sun and Moon, but you could still access some Mega Evolutions after beating the games.

In order to play a Mega Mewtwo, you first have to transfer the character from another game. Mewtwo does not appear in Sun and Moon, so you’ll have to use the Pokémon Bank app on the 3DS to move a Mewtwo from a game he does appear in, like X, Y, Red, or Blue.

When you have a Mewtwo, you’ll need to use Sun and Moon’s Mystery Gift feature to get the Mega Stones that let him transform. You have to enter the code M2DESCENT to get the stones, which you then collect in the game from the delivery man in any Pokémon Center.