Dragon of Prismore

This is the monster from the Myth of Bolden.
It's description varies between different variants, some of the oldest variants describe lizard-like feet and serrated teeth, whereas slightly newer variants commit to a draconic lizard, crocodilian, bear, but it is commonly stated to be a dragon. The crystal-like appearance of the creature is almost always illustrated as identical to that of Prismore Caverns' crystalline walls, saying the monster's "scales" mimic the glowing patterns reflected off the ores. Others posit the monster's armour is made of the same ore, which gives it the similar properties, and others state the creature has powerful illusionary magic or other manipulation or onlooker's perceptions.
This creature does not solely appear in the Myth of Bolden, and has various texts dedicated to its existence. These texts are scarce, so their contents are not widely known. However, its infamous depiction in the Myth of Bolden leads to many citizens of Excabridge believing in its existence, including Mayor Eryian, but this may be to keep up appearances for the children who are guided away from dangerous behaviour by the alleged "Dragon of Prismore".