Catha

Catha is the larger and closer of Exandria's two moons, considered the primary moon. The phrase "lunar cycle" commonly refers to Catha's cycles. It is associated with Sehanine, the Moon Weaver.

Though often depicted close to each other, Catha and its counterpart Ruidus have different orbits and can appear in different points in the sky.

Description
Catha appears either pale blue or bright white in the sky, resembling Earth's moon, though Catha is a little closer than the moon is to Earth and so appears larger in Exandria's sky. It takes between 30 to 40 days to orbit Exandria, during which it waxes and wanes; this is the commonly referred to lunar cycle. The brightness and phases of Catha are constant and predictable respectively. The surface of Catha is pocked with craters. It is also implied to be tidally locked to the planet it orbits, much like Earth's moon.

Catha appears in the sky in both the Feywild and the Shadowfell, due to both the Material Plane's proximity to the other two planes, and the influence of the Moonweaver.

Symbolism
Catha functions as a symbol of the god, Sehanine, the Moonweaver. Most believe Sehanine created Catha to "bless the just with cunning and caution" and to cloak those who need "stealth and subtlety." Other followers of Sehanine identify Catha with "the Moonweaver's cunning and grace," posing an alternative to the general association of the deity with trickery and illusions. They understand the light of Catha to favor the "goodhearted." While the light of Catha can hide, its connection with revelation is also prevalent. Folklore holds that Sehanine grants her worshippers who invoke Catha "inspired dreams" and knowledge of "hidden paths." A small Syngornian sect of the Moonweaver derives a moral imperative from the predictability of the lunar cycle to safeguard balance and calm order in the world. Furthermore, Catha's association with balance and order leads this sect to juxtapose Catha with the "ill-fated chaos of Ruidus."

Astronomy
Elven astronomers track the lunar cycles of Catha to predict the largest full moon of the decade, during which night the followers of Sehanine observe her holy day.

Magical phenomena
Catha's lunar cycles affect entities with bestial curses, especially nocturnal creatures. Furthermore, the lunar cycle of Catha rather than Ruidus influences entities with lycanthropy, changing their shape involuntarily under the influence of a full moon. In addition to curses, Catha's light can interact with necromantic magic during the full moon phase. As of at least 836 PD, reports exist of Catha's light coinciding with the raising of undead soldiers from the Battle of the Umbra Hills in Tal'Dorei.

Extraplanar phenomena
The lunar cycles of Catha connect to other beings, which may include demons per the speculation of Cobalt Soul archivists and others. Some worry that rare double solar eclipses, in which both Catha and Ruidus eclipse the sun simultaneously, cause the Material Plane and other planes to intersect calamitously.

Trivia

 * While more references to the "moon is made of cheese" trope exist for Ruidus, Taliesin does jokingly identify Erwin Schrödinger as "the guy who invented cheese on the moon."
 * Catha drawn by Critical Role official artist Clara Daly has close similarities in its imagery to Earth's Moon. Catha has a series of dark spots on its northern, north-eastern sides that share a pattern with lunar mares. Catha also has two prominent craters painted with sunbeam-like lines, locations of which aligned with the Moon's Tycho and Copernicus craters.