The Ryuusazai (リュウサザイ) is a creature that lives in the 6th Layer of The Abyss where return is humanly impossible.
First documented in the notes of the white whistle Lyza "The Annihilator", it is a creature resembling a horse with a long neck and what appears to be a beak. Its skin is covered in scales like a reptile, making it an odd mixture of different kinds of animals. When it receives an impact, its scales will break off. Furthermore, they're laced with a dangerous poison.
Males often engage in fights with one other, tackling each other tenaciously ignoring the curse and moving in a three-dimensional manner. Its towering size comparable to that of a large dinosaur makes for an imposing figure, and they're considerably strong creatures, the danger level of a single individual is said to equal to that of an entire swarm of Kuongatari. They don't appear to be particularly violent however, so if not provoked a safe passage is feasible even around their vicinity.
Just like the Gogouge and Inbyo, when its territory is breached, the Ryuusazai will tail and attack the intruder. When in close range, it uses its long rigid legs to stomp and impale the perpetrator. They were even able to chip the strong metal that makes up Reg's arm. When out of range, its proboscis-like appendage will open up and it will spit out a projectile, a mixture of rocks and something slimy.
- One of the beasts of the Abyss that can damage Reg's body.