Moss Rock

A Moss Rock (Japanese: コケでおおわれたいわ moss-covered rock) is a moss-covered rock that enables Eevee to evolve into Leafeon.

A Moss Rock in Pokémon Adventures

In the core series games, if an Eevee is leveled up in an area containing a Moss Rock, it will evolve into Leafeon. Even if Eevee meets other evolutionary conditions when leveled up, the Moss Rock will still cause it to evolve into Leafeon rather than Espeon, Umbreon, or Sylveon. In Generation VIII, this mechanic was replaced by using a Leaf Stone to evolve Eevee into Leafeon.

In the core series games

In Sinnoh, a Moss Rock is located in the southwestern section of the Eterna Forest, to the west of a formation of trees that resembles a sideways L. Eevee cannot evolve if the player is in the Old Chateau or the path that encompasses the outskirts of Eterna Forest.
In Unova, a Moss Rock is located in the southwestern section of Pinwheel Forest.
In Kalos, a Moss Rock is located on Route 20.
In Hoenn^ORAS, a Moss Rock is located in the northeast of Petalburg Woods, behind a tree that can be cut.
In Alola, a Moss Rock is located in the northern section of Lush Jungle, directly north and slightly east of where the player enters.

As the Moss Rock is not present in Kanto, Johto or Galar, Eevee cannot evolve into Leafeon at all in HeartGold and SoulSilver; it can only be obtained by trading it from Diamond, Pearl, and Platinum. In case of Pokémon Sword and Shield, these can be evolved by using a Leaf Stone on them.

Appearance

Sinnoh	Unova	Kalos	Hoenn	Alola

In spin-off games

Pokémon Mystery Dungeon series

Due to the Moss Rock's absence in Pokémon Mystery Dungeon: Explorers of Time, Darkness and Sky, Eevee evolves into Leafeon through the use of the Mossy Rock. It evolves by the same method in Gates to Infinity.

Pokémon Conquest

In Pokémon Conquest, Eevee evolves into Leafeon when it is deployed in Greenleaf while it has a Defense stat of 94 or higher.

Pokémon GO

Because Pokémon GO uses real-world locations, being within range of a Pokéstop outfitted with a Mossy Lure Module is required to induce evolution in Eevee.

In the manga

Pokémon Adventures

Diamond & Pearl arc

A Moss Rock appeared in Ring Around the Roserade I. Diamond found one as he, Pearl, and Platinum traveled through Eterna Forest. Liking how cool the stone felt, Diamond, Lax, and Tru decided to take a nap on the Moss Rock, only for Pearl and Chatler to tell them to keep moving.