Lugia is a large Pokémon that resembles a dragon, a plesiosaur, and a bird. It is primarily silver-white, but it has blue undersides with slightly varying tones. It has a ridged mouth similar to a beak, although it has pointed teeth on its lower jaw. Its head has a point to the back, and Lugia's eyes have pointed blue or black spikes on them. Lugia has a long, slender neck and a smooth, streamlined body. Dark blue or black plate-like protrusions run down the length of its back, and there are two smaller, more pointed ones on the end of its tail. It can fold back these plates to increase its speed. Lugia is covered in many scales that protect it from attacks. It has large wings that resemble hands. Though it is gender unknown, a young Lugia has been observed, suggesting there is a breeding population. Lugia has been shown to be fiercely protective of its young.

Lugia leads the legendary birds. When they fight over territory, Lugia is the only Pokémon that can quell their ceaseless fighting, as observed in the second Pokémon movie. Much like the birds, it possesses the ability to control the weather; most notably, it can calm and give rise to storms. It is said that a light flutter of its wings is capable of causing winds powerful enough to tear a regular house down. If it were to flap its wings, it could hypothetically spawn storms lasting as long as 40 days. It is highly intelligent, and because of the devastating power it could accidentally inflict, it isolates itself deep underwater and tends to sleep in solitude. It is extremely rare and is hardly ever seen. Lugia has been referred to as the guardian of the seas. There are rumors Lugia would appear during the night of a storm. Lugia loves Lugia Treats made by Snacksworth, who once encountered it in the past.

Forms

Lugia has an alternate form called Shadow Lugia. It has jagged silver eye-spikes, a dark-purple body with white undersides, and glowing red eyes. It also has sharper toes that resemble claws, as well as a longer, more pointed tongue. Additionally, due to the shape of Lugia's back plates on its 3D models being changed after Generation IV, Shadow Lugia now posesses a unique design for them.

(Source: Bulbapedia)