River serpents are descended from normal, if large, snakes who lived in the rivers and lakes of the Successor States of Rega. Warped by the corupting influence of the Blood of Invidia, sometimes by direct exposure, somtimes via dragon's blood, they have become Draconic predators themselves, preying on large water creatures and any hapless boats or swimmers they might encounter. Despite their size, they are very stealthy, and often surprise their victims.

sheet here https://www.patreon.com/posts/86404634