Celesteela is a large, vaguely humanoid Ultra Beast with a bodily construction that resembles a cross between a space shuttle and a bamboo shoot. It has a small, white head with a tiny mouth and a skinny neck with three segments. On top of its head is a gray structure resembling a hat with long, flowing hair underneath. The hair reaches midway down its body and is rimmed with bright blue. The "hat" has two small blue dots and four white spikes arranged in an X-shape. These spikes resemble decorative hair sticks. On the very top of its hat is a long gray horn similar to a drill bit. It has large, disembodied gray arms that resemble bamboo stalks. At the end of each arm is a ring of bright blue, fin-like projections and a collection of eight smaller, black bamboo shoots. Each smaller stalk has a bright blue ring with a small line extending back up the stalk.
Its main body is conical and resembles a dress with four overlapping layers. The shortest and outermost layer is the shortest and appears metallic, while the inner layers are each a lighter shade of green, progressively longer, and seem to be cloth or plant material. Underneath all the layers is a white body with a light gray crisscross pattern covering it and a bright blue ring along the base. Below the dress is what appears to be a collection of eight black bamboo stalks. On the bottom of each stalk is a bright blue ring with a small line extending back up the stalk; this causes the stalks to also resemble solid rocket boosters. Celesteela is one of the heaviest Pokémon, tying with Cosmoem.
Celesteela live in another world named Ultra Crater. According to Wicke from the Aether Foundation, its most distinctive feature is the energy that it stores within itself: a flammable gas that it can shoot from its two huge arms. This is mostly used to propel itself in flight and for battle, but it is thought to have sufficient power and lift to even fly into space. Celesteela's rocket thrust is powerful enough to destroy an entire bamboo forest. Despite being a Steel type, Celesteela's body is plantlike and can absorb nutrients from the soil. Like all Ultra Beasts, it stores an energy within its body similar to the aura seen around Totem Pokémon. This energy is called Z-Power. As seen in the anime, Celesteela can have a long lifespan, as one was buried in Alola for over 200 years.
Celesteela debuted in Rise and Shine, Starship!, where Sophocles found it buried alive while camping at Bamboo Hill and believed it to be The Celestial Starship (Japanese 星舟かぐやStarship Kaguya), a figure from a folktale. He and his classmates decided to dig it out of the ground, and although the Ultra Guardians failed to catch it due to the fact that it was rooted down, it eventually flew off back into space. Unlike the other Ultra Beasts in the anime so far, this Celesteela had been growing in Alola for more than 200 years.
Celesteela may be based on Princess Kaguya from The Tale of the Bamboo Cutter, which was said to have been discovered as a baby inside a bamboo stalk, and was revealed to hail from the Moon. This may be referenced with Celesteela's design, which seems to visually combine bamboo shoots and trunks with elements of a space shuttle, and a depiction of Princess Kaguya as a woman with long hair wearing a multilayered kimono. It may also be referenced with the fact that Celesteela is exclusive to Pokémon Moon and Ultra Moon.
Celesteela's body may also incorporate similarities to the spacecraft SELENE (nicknamed "Kaguya" in Japan), which orbited the Moon between 2007 and 2009. The combination of bamboo and spacecraft elements may also reference bamboo rockets.
Celesteela may be a combination of celestial, steel, and stella (Latin and Italian for star).
Tekkaguya may be a combination of 鉄火 tekka (gunfire), 鉄鋼 tekkō (steel), and かぐや姫 Kaguya-hime (Princess Kaguya).