The Jishin-uwo cryptid is actually the legendary Minhocao from South American mythology. It made its first appearance in Life in the Underground which is season 2 of 2010 TV series called The Secret Saturdays. The Minhocao is described as an enormous earthworm easily reaching 80+ feet in length with a diameter of 3-4 ft. wide. Most interpretations of the Minhocao include it having tentacle-like structures coming out of its head. (We see these as "feelers" that the creature uses to detect vibrations in the ground.)
Due to its enormous size and amphibious nature, the Minhocao is often blamed for over-turned boats and cars, collapses houses and trenches, etc. The Minhocao is a subterranean cryptid that is known for its enormous underground passageways, being true to its worm-like nature. This creature is also big enough and capable enough to eat anything and everything it wants to, especially large livestock and wild animals.
The Minhocao, along with other South American cryptids, were trying to relocate and stock up in fear of Kur coming back. The Minhocao were the ultimate tunnel-diggers for the rest of cryptids, being their main source of locomotion. Zak realized that the cryptids were stealing goods and relocating in fear of him, so he communicated with them and reassured them that he wouldn't hurt them.
In War of the Cryptids, we can assume that Zak won over the cryptids' trust, because we see Zak and the others using the Minhocao as means of locomotion and support.