The Thunder Horse is a cryptid that was only seen in the video game The Secret Saturdays: Beasts of the fifth sun, in the DS version.
The Thunder Horse is a large, grayish, and dotted equine. This huge cryptid's hoof-beats were said to be the origin of thunder. This creature's indestructible hooves allow it run over spiked surfaces. This creature is also known for killing bison as a self defense. The early Indians of central-north America were shocked at the immense size of this beast.
In the ice cavern level of the DS version of the video game, Zak has to ride the thunder horse over-top the icicles.