The Rympth is a serpent-like creature native to Va-nah: the inner surface world of the Moon. It is a crawling reptilian being, with poisonous flesh and thus considered inedible by the Va-gas, although it is preyed upon by the Tor-ho, which is presumably immune to its toxins.
The Rympth's body is about five feet in length, shaped like an Earth snake and likewise moves in an undulating fashion, but it also has two pairs of small legs similar to a frog's. The head is flat and contains a single eye on its center. They are also amphibious in nature, being as agile on land as underwater.
- The Moon Maid, by Edgar Rice Burroughs (1926) (First appearance)
- The word "Rympth" is also used as an insult among the U-gas.