Turnbetl

Turnbetl was the largest and closest satellite of H'Catha, the farthest planet from the Sun in Realmspace.

Geography
The spherical moon orbited H'Catha along the plane of the flat disc in a very eccentric orbit, with a perigee distance of and an apogee of. Its proximity to H'Catha generated tidal forces that kept the planet's ocean in a gentle and continual circulation.

The moon's atmosphere was extremely unstable, composed of highly reactive gases that immediately exploded upon contact with oxygen. The typical atmosphere of a medium-sized spelljammer could produce an explosion several times stronger than a fireball cast by an experienced wizard―enough to be decidedly lethal.

Defenses
Due to the extremely dangerous nature of Turnbetl, it was recommended that the moon be kept in quarantine so travelers did not approach it.