The Giant River Wyrm might seem to the untrained eye to be a lone giant monster, but in fact it is anything but. It starts as one of more then a hundred eggs within a large egg sac within a reasonably fast flowing and clean river. Despite their jelly-like appearance, the eggs are tasty and good to eat both to humans and to fish, but an adult Giant Wyrm is coiled around them underwater ready to eat anything or anything that comes near. Such coiled Wyrms should never be approached no matter how beautiful they look, and never try to feed them. People have died that way when they get too close.
The juvenile Wyrms look very much like large tadpoles when they hatch, and after eating the egg yolk they turn on each other until only around ten to twenty are left. After this they switch to chasing and eating salmon or other fish, some of which they eat on the spot, others being brought back in a constant stream by members of the colony at any one time to their giant parent, which, old and stiff compared with the juveniles, finds it hard to hunt for itself. When it does so, it lies concealed underwater, able to sense through grooves in its nose if something like a deer is drinking.
It attacks by leaping out of the water, grabbing the victim with its beak full of huge teeth and fangs and dragging it into the water, where it coils itself around the victim and holds it underwater until it drowns. It can attack anything up to the size of a fully-grown deer, which will feed it for weeks on end. However, should it fail in its attack it has to go back to its river, as it cannot move well on land.
In the mating season they shed their normal dull colouration and their scales catch the light and shine with every colour of the rainbow, a sign that they are fertile and ready to mate. When a male meets a female their long complex fertility dance is a sight to behold. When two of the same gender meet each other they put on a threat display, stretching out of the water, hissing loudly and measuring each other.
Only if they are exactly the same size will a fight to the death break out, with the winner cannibalising the loser, otherwise the loser slinks away. When not in the mating season, each adult Wyrm sticks to his or her section of the river.
Some rich villains or nobles with more money then sense have tried capturing these adult Wyrms alive and placing them in pits or ponds as traps. Not only is this very hard to do, but away from their juveniles, they will sicken, grow crazed with hunger and, if not fed very often with fish, will die within weeks or months. It is not worth the trouble and expense of capturing and transporting them.