5th dnd – Creature lizard breathing lava (to worship)

I'm trying to find a creature worshiped by a cult for my character, and since I'm not particularly creative, I decided to steal Team Magma at the third-generation pokemon.

For strangers, the cult loves the legendary pokemon Groudon, a giant lizard / creature resembling a dinosaur with abilities centered around fire and lava.
Is there a creature that already exists in 5th that can serve as an equivalent, or do I have to create one myself?