From PathfinderWiki
Type Magical beast
CR 7
Environment temperate hills

Source: Mythical Monsters Revisited, pg(s). 8

The orthrus is always male. It resembles a two-headed wolf or dog, whose tail ends in a dragon's head. It, along with the female legendary chimera, was created by Lamashtu to be the ultimate predator. Some of their offspring became the modern chimera but the two monsters normally view each other with hatred.

In many ways they are similar to chimeras, but they cannot fly as they lack wings. Their dog-like claws are not suitable as weapons, but each of their heads has a powerful bite and opponents grasped in two or more heads may be ripped apart.

The placement of their heads gives them the ability to see all sides at once.[1]