H3Oionien
H3Oionien is a fictional planet featured in the *Halo* multimedia franchise, created by Bungie Studios and later expanded by 343 Industries. The planet is depicted as a lush, tropical world with dense jungles, towering mountains, and vibrant ecosystems, serving as a key location in the *Halo* universe. Its name is derived from the chemical formula for a hydronium ion (H₃O⁺), reflecting its role as a water-rich world, though the exact origin of the name in-universe is not explicitly explained.
H3Oionien first appears in the *Halo: The Fall of Reach* novel series, where it is introduced as
The planet’s environment is described as heavily influenced by its water-rich atmosphere, with extensive rainforests and
Fans of the *Halo* series have speculated about H3Oionien’s potential as a future setting for games or