Alright! Day 2. Ended up being pretty proud of this design and lore.

[I'm following this prompt list for the month]

Bio:

Turunctus is one of many so-called "Dragon Slayers" from Europe's history. Though most have crumbled into dust by now, few of these mighty constructs remain, all of them having castles of varying sizes on their backs. They range in size massively, some being essentially a single turret with legs, while others are entire castles. Some ancient texts and drawings imply that the largest of the Dragon Slayers was the size of an entire castle town. Though looking quite drab with bare stone now, it's likely that all Turunctids were painted as old castles used to be.

All Turunctids are powered by the glowing crystals under their bodies, which range in colour from bright yellows to dark reds, some even being marbled with different colours. It's unknown if the hue matters much, but this does affect the colours the Turunctus' attacks. Their offensive abilities, other than their club tail lies in the various "windows" in the castles on it's back. If required, they can shoot some sort of arcing laser or energy shot out of any of the windows of their choosing.

Little remains today of those who have fallen, meaning either that most were destroyed until nothing was left, or that more remain dormant, hidden in caves or at the bottom of lakes.