Illsertis is an Elder Dragon that dwells in watery regions.
The main body of Illsertis is covered in a hard orange shell, while some openings and the rest of the body sport a softer fish skin, its face looks like that of a canid with dark blue and red frills around it, sporting sharp teeth and claws, and a powerful water sac, it is able to unleash the rage of the deep to those who wish to risk their lives.
- Water Jet: A fast, metal cutting jet of water from its mouth.
- Wing Booster: Illsertis will propel itself upwards with a stream of highspeed water coming out from openings in the wings, and then using more openings it will launch itself towards a target, slashing it with both the high speed water streams and the claws.
- Pin Bite: A simple bite, a hunter caught in it will be pinned, if you manage to release yourself you will be afflicted with severe waterblight and defense down.
- Physical Attacks: Normal attacks such as slashing with claws, weaving the tail, ramming hunters or jumping on top of them.
- Armor Re-Growth: When the armor is broken, it can repair itself one more time, this new armor can't be broken, but is less effective and white in color.
- There are stories of Illsertis coming back to life, with 2 new heads growing much like an hydra, this hasn't happened to the recovered specimens, but the guild doesn't discard the possibility of a subspecies that is long extinct, or very hideous.
- Aside from the Unknown Island and Drowned Wetland, it is known for attacking ships in the sea, usually being very brutal against people, the few survivors have met long and painful death later due to infections.