Prince Rutherford is a short-tempered male Yak, and the current ruler of the northern country of Yakyakistan.
Appearance
Rutherford is a very large, ginger-colored yak with shaggy fur that covers most of his body, including over his eyes.
His outfit is notable for wearing numerous golden accessories: He wears golden rings along his hooves, horns, and beard, along with a set of golden bell earrings and a golden drape on his lower back and tail. He did have a single small ring on the tip of his horn, which he willingly gave to Garnet as a token of friendship. His Yak hump is also draped in a dull blue saddle blanket. He wears a black flower-shaped crown on his head.
Personality
Rutherford is shown mainly as very loud, and short-tempered. He does have enough of a level head to meet with other nations on calmer terms, but will quickly go into a destructive rage if anything displeases him, even down to the simplest of things. He still is capable of holding himself back on his anger though if told the right information, shown when Cadance and Luna tell him they couldn't perfect Yakyakistan food first before he tried their food.
Despite his temper, he still has enough culture to appreciate music, even going into tears at The Ponytones' performance.
History
My Little Universe II
Prince Rutherford first appears in "Tongue-Tied" as apart of the Yakyakistan representatives to Equestria. On arriving, he declares his hopes of having a good friendship between Ponies and Yaks, being friends for a thousand moons. After his banquet meal in Canterlot, he requests to go and visit Ponyville, as he and his Yaks heard that it's exciting there and wanted to see it for himself. During his visit in Ponyville however, he and his Yaks begin to constantly destroy anything and everything that even remotely disturbs or angers him.
He first destroys the Ponyville Café after the flowers strung up for Ruby and Sapphire's date make him sneeze. Next he was offered by Applejack and Pinkie Pie a place to sleep at Sweet Apple Acres, but he and his Yaks destroy the barn as the beds made for them weren't made of Yak hay. This pattern continued throughout their visit: attacking Fluttershy's animal friends after thinking they tricked him, Rarity's Ponyville Boutique when they didn't find Yak fabric, even attacking Rainbow Dash's "Yak snow" as it wasn't Yakyakistan snow. After believing he was tricked by The Ponytones of actually singing good music, he became so frustrated that he decides to leave, and declare war on Equestria. However, before he could leave, he was met up by Pinkie Pie, and brought to their party Ponyville was planning. Once he got his spirits lifted by both Pinkie Pie and Spinel, he calls off his declaration of war and becomes good friends to the ponies, giving one of his gold rings to Garnet as a token of their new friendship.