Threehorn Peak, as already mentioned, has a top shaped like a Threehorn's head. Inside is a large cave full of magma, which is crossable due to rocky bridges. It has several "floors" or layers; one of these floors has green magma. Far down below it, there is at least one underground river, that boils with extreme heat. The three "horns" on top of Threehorn Peak spew lava when the mountain erupts.
Threehorn Peak has so far only appeared in The Land Before Time VII: The Stone of Cold Fire. It is first shown when Littlefoot, a young Apatosaurus, sees a glowing blue stone land on it. Later, some Rainbow Faces reveal the stone to be a "Stone of Cold Fire". They explain that the stone is thought by many to have powers "far beyond [their] comprehension." Pterano, a Pteranodon along with his two henchmen, Rinkus and Sierra, want to get to the stone in order to have its "magical powers" and rule over the Great Valley. They, however, don't know that the stone landed on Threehorn Peak. Pterano gets his nephew, Petrie, to ask his friends where the stone landed, but when his friends find out the reason he asked, they become angry with Petrie, because though they don't know Pterano's true intentions, still don't trust him. Later that night, Ducky feels bad for Petrie, and decides to go cheer him up. While she is walking, she overhears the Flyers' plans. The flyers catch her eavesdropping, and in order to stop her from telling their plans, kidnap her and take off immediately. Ducky however tries to escape when they land, and falls into a small cave.
After traveling for quite a while, Littlefoot, Cera, Petrie and Spike find Ducky, and decide to head to Threehorn Peak to stop the Flyers. Eventually they get there unintentionally during a rainstorm (which slowed down the trio of Flyers), when they enter a small cave to get shelter. The cave turns out to be a way into the base of Threehorn Peak. After a short snooze they find a pile of green food lying next to them, and after eating some of it wonder who left it. They then see a figure and chase it up several "floors" of the smoking mountain, discovering it is a Rainbow Face in the process. After catching the Rainbow Face they find it is the male of the two Rainbow Faces that told Littlefoot about the Stone of Cold Fire. After the two Rainbow Faces argue, they decide to help the gang. They do this by pushing away a boulder to reveal a vent which a rock is shown to be blocking. The gang climb onto the rock, and are pushed up to the top of the mountain by steam coming from an underground river. Once and the top, the children find a trench gouged out in the mountain, and follow it to the Stone of Cold Fire. The flyers arrive soon after them. After Pterano can't do anything with the "magical" stone, Rinkus and Sierra overthrow him and start pounding the rock; telling it to show them its power. However, it still does nothing, and Threehorn Peak starts rumbling. Before it erupts, Petrie's Mother and a Quetzalcoatlus arrive, and along with Pterano, help the children escape just before the eruption. The Stone of Cold Fire blows up, sending Rinkus and Sierra flying burnt and bruised back to the ledge they had camped in during the rainstorm. This is the last time Threehorn Peak has been seen in the series.
- On the Nickelodeon cartoon franchise Avatar; an episode from the Legend of Korra shows from the background a mountain that looks like Threehorn Peak. This is the second time Nickelodeon has made reference to The Land Before Time in years, the other being the Fairly Odd Parents episode "The Land Before Timmy".