dnd 5e – Lizard creature breathing lava (for worship of cults)

So I'm trying to find a creature that is adored by a cult for my character, and since I'm not particularly creative, I decided to cheat the Magma Team from the third generation pokemon.

For those who are not familiar, the cult worships the legendary PokΓ©mon Groudon, a giant lizard / dinosaur like a creature with skills centered on fire and lava.
Is there any creature that already exists in 5e that can serve as equivalent or do I need to create one myself?