It is not known to evolve into or from any other Pokémon.
It is often considered to be closely related to Lugia as a duo, even sometimes as its polar opposite. Silver represents Lugia as "guardian of the seas", and Gold represents Ho-Oh as "guardian of the skies." Ho-Oh is also the trio master of the Legendary beasts.
Ho-Oh is the game mascot of Pokémon Gold and its remake Pokémon HeartGold, appearing on the boxart of both.
This section temporarily contains information copied directly from Bulbapedia, and needs to be rewritten so not to be classified as plagiarism.
Ho-Oh is an avian Pokémon resembling a phoenix and a peacock. Its feathers are predominantly gold and red, with yellow tail-feathers, a white underside, and green feathers at the tip of its wings. Ho-Oh has a green stripe on its neck, a yellow beak, black rings around its red eyes, and a feathered, yellow crest on its head. Ho-Oh's wings are prismatic, causing it to trail a rainbow behind it. It has darkly colored feet and legs with four toes and long talons.
Ho-Oh has a mythical power to resurrect the dead. Ho-Oh was the only known Pokémon to learn Sacred Fire, its former signature move. It is said that when it flies its huge wings create bright, colorful rainbows. The rare few who bear witness to Ho-Oh are promised an eternal happiness. Ho-Oh used to perch at the top of the Bell Tower (or Tin Tower) until the Brass Tower was destroyed by fire. It now presumably flies through the world's skies in search of a Trainer with a pure heart.