Altaria is a blue, avian Pokémon. Its body and cloud-like wings are covered in fluffy, white feathers. It often folds its wings behind it, obscuring its back. Two long, blue plumes extend like streamers from the back of its head. It has a short, hooked beak and prominent cheek patches, both of which are white. Additionally, it has beady, black eyes. It has a long neck and short legs protruding from its fluffy body. The feet are blue with four toes, three claws forward and one backward. The tail is made up of five feathers, the outer two being longer than the inner ones.
Mega Altaria has more extensive cloud-like plumage, with a large, fluffy mass extending from its back. The feathers have grown as a self-protective measure, and they glimmer with an iridescent sheen. Its cottony wings are more distinct than in its base form, and its blue belly is now exposed. Additional fluff surrounds its neck like a collar, and its head is adorned with a hat-like crest. A single, small feather curls out from its forehead, though its facial features are unchanged. Its tail feathers have grown into a long, wavy streamer, with three longer central plumes. Mega Altaria's singing voice is even more beautiful than that of its regular form. It is known for its sociable personality and is not timid.
This Pokémon uses its wings to catch updrafts and soar across the sky. It gracefully glides through the clouds, often while singing or humming in a soprano voice. Its voice seems to have special properties which induce a dreamy state for listeners. Altaria can be very affectionate, enveloping people it has bonded with in its cotton-like wings. Altaria is often found living in forests, though it also inhabits mountain ranges.
Two Altaria appeared in a flashback in Drayden Versus Iris: Past, Present, and Future!. One of them was a Pokémon that students from the Opelucid Academy could borrow in order to learn how to battle. The other was one of the Pokémon that Iris had befriended.
This makes Mega Altaria the only Mega Evolved Pokémon with a unique type combination.
Mega Altaria is also the only Dragon-type Pokémon immune to Dragon-type moves.
Altaria is the quickest Dragon-type Pokémon to reach level 100, needing only 600,000 experience points to do so.
Altaria is likely based on a Peng, a Chinese legendary bird of enormous size, said to travel 3000 li in one flap of its mighty, cloud-like wings. It is often portrayed as having a fish's head and whiskers.
The shape of the fluff on Mega Altaria's head may draw inspiration from ushankas.
Altaria is a combination of alto (Spanish, Portuguese, and Italian for high) or altus (Latin for high) and aria (Italian for air). Aria in music can refer to expressive melody, relating to Altaria's singing abilities. "Ria" could additionally be a misspelling of Rhea, the name of a large white bird. It may also refer to the star Altair, the brightest star in the constellation Aquila, the Eagle.
Tyltalis may refer to Tyl—also known as Epsilon Draconis—a star in the constellation Draco, the Dragon. It may also be a reference to the play L'Oiseau Bleu (The Blue Bird) by Belgian playwright Maurice Maeterlinck. The story is about two siblings, Mytyl and Tyltyl (ミチル Michiru and チルチル Chiruchiru in the Japanese translation of the play), who are tasked with finding the "blue bird of happiness."