Orthrus

Orthrus is a creature in Greek mythology, a two-headed dog and a doublet ("brother") of Cerberus, both whelped by the chthonic monsters Echidna and Typhon. He descends from hell and is one of the strongest summons seen so far,Orthrus is so big that it towers summons such as Baku and Gamabunta.

Appearance
It is a gigantic dog with two heads covered with a white skeleton like substance, large enough to dwarf Gamabunta and Baku. It has panther-like limbs and a spiky tail. It is predominantly light orange in colour with the exception of its white skeleton, legs and the markings around its eyes.The claws possesed by Orthrus is sharp enough to tear through a susanoo.

Abilities
Orthrus has the ability to breathe flames and manipulate fire around him, When it opens its mouth and inhales, it can create a powerful suction that sucks in everything within a large radius, while at the same time exhaling through its mouth.Orthus can also summon the gates of hell and drag an enemy to hell along with him. Orthrus also posseses great amount of chakra reserves such that it can give a tailed beast a competetion.