Deep Dragon

As one would expect, deep dragons are found deep, deep in the earth. It's not completely certain whether deep dragons are their own species, or some kind of mutated version of a true dragon. Regardless, they're just as powerful as true dragons. Surface dwellers may now give a sigh of relief as it's made known that deep dragons have no interest in leaving their dark world. They sometimes make pacts with drow, but that's mostly to keep an eye on them and make sure that whatever the drow do, it won't interfere with the deep dragon's well-being.

Deep dragons cannot be trusted. They’re especially tricky creatures, and similarly difficult to fool. Even a wyrmling is born with innate true seeing, making them immune to the effects of illusions and invisibility. Older deep dragons become more attuned to their cavernous and stony environment. They start out being able to easily burrow through stone and worm their way though small cracks. By the time end of their lifespan, deep dragons can command the stone to open, close and warp as they please.

Why fight some repugnant humanoid skulking in the tunnel you've left behind when you can simply command the tunnel to seal itself, crushing the intruder?

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