Xixtchil is a plant-like life form native to the planet Venus, which is mostly known for its commercial value and strange medical properties.
From the spore-pods of xixtchil is extracted xixtline (properly known as trihydroxyl-tertiary-tolunitrile-beta-anthraquinone; or "triple-T-B-A"), a substance notable for its rejuvenating effects on Humans. When consumed, it produces a perfectly youthful appearance. However, it does not affect the user's natural lifespan, resulting in that the seemingly young person will eventually die of old age anyway.
- "Parasite Planet", by Stanley G. Weinbaum (1935)
- "The Planet of Doubt", by Stanley G. Weinbaum (1935) (Mentioned only)
- "The Red Peri", by Stanley G. Weinbaum (1935) (Mentioned only)