The griffin is a mythological eagle/lion hybrid, and an antagonist in Gravity Falls.
The griffin appears among a group of fantasy creatures from the game Dungeons, Dungeons, and More Dungeons, that faces off against the Pines family and Grenda in "Dungeons, Dungeons, and More Dungeons", when its group kidnapped Dipper and Ford. At the end of the episode, it is seen kidnapping Toby Determined, but it is unknown if this is the same griffin that carried Dipper and Ford into the forest or if it is another griffin, because at that point Probabilitor the Annoying and his crew had already been sent back to their dimension.
The griffin is a half eagle half lion creature with yellow eyes, large wings, with darker edged feathers. A dark tan bottom half of his torso the top half is mostly feathered with a dark gray beak and large eyebrows. The closer to the lion half of its body the more tan colored his feathers are. Its front legs are the same color as its beak, with lighter grey claws.