Arimaspi is a giant monster in the shape of a mountain goat, except that he can stand up-right, had claws, and a single eye. He was also adorned with several golden accessories, further expressing its greedy personality.
In the episode "The Lost Treasure of Griffonstone", his story is explained by Grampa Gruff, and shown in a flashback: Arimaspi stole the Idol of Boreas, which united the griffons of Griffonstone. King Guto and his griffons tried to fight him, but he overpowered them and escaped out the window. He then tried to escape by crossing a bridge above the Abysmal Abyss, but was cornered by the griffons. Suddenly, the bridge was struck by lightning, sending him falling to his death and taking the idol with him.
Later, as Pinkie Pie and Gilda try to save Rainbow Dash from falling into the Abysmal Abyss when she is injured trying to recover the idol, they reach a lower area where Arimaspi's skull can be seen next to the idol.
- Arimaspi is based and named after a race of mythological one-eyed people who fought griffons over gold.
- He looks similar to the G1 villain Grogar, as he has a goatlike appearance.
- His fall is similar to that of the Evil Queen and Durin's Bane the Balrog, except that the Balrog survived.
- Arimaspi is the only villain that the main protagonist(s) don't face directly, and is the only one that is confirmed to be truly deceased (unless you count King Sombra, whose death was confirmed by Meghan McCarthy though this continues to be debated).
- According to an updated map of Equestria, Arimaspi is the name of its species, which holds territory southwest of Macintosh Hills.