The Hadhayosh is a land creature from ancient Persian mythology. In the Avesta it is also called the Sarsaok. In the 14th century, it was said to have raided Iran, giving itself a name as a fearsome beast.
The Avesta is one of the very few texts which reference the creature, describing it as a primeval ox:
Of the ox Hadhayosh, which they call Sarsaok, it says, that in the original creation men passed from region to region upon it, and in the renovation of the universe they prepare Hush (the beverage producing immortality) from it.