Masquerain is a light blue Pokémon with two pairs of rhombus-shaped wings on each side of its body. Its head is shaped like an elongated teardrop with a pink face and round, black eyes. On either side of its head is a large antenna that resembles an angry eye. The antennae are white with pink along the lower rim. White lines along the rim resemble eyelashes, while a large, dark pink dot in the middle represents the pupil or iris. These eyespots are used to intimidate enemies.
Masquerain's four wings allow it to fly in any direction and hover, but it cannot fly when its wings are wet. Additionally, rainy weather causes its antennae to become heavy and droop. In order to protect its wings and antennae, this Pokémon will shelter under trees or the eaves of houses. Masquerain lives on water's edge.
In Dewpider Ascending!, a Masquerain was living near the Pokémon School as a Surskit. Surskit evolved during a battle against a Dewpider over its territory. The battle ended when Masquerain, pleased with its evolution, flew off and allowed Dewpider to live near the Pokémon School.
Masquerain can be seen as a counterpart to Araquanid. Both share the Bug type and the same base stat totals, and both can be found at Malie Garden in Pokémon Sun and Moon, taking the place of the other depending on the time, with Masquerain being found during the night and Araquanid in the day.
Furthermore, Masquerain and Araquanid share the same base stat total of 454. In fact, this reflects a 40-point boost across Masquerain's original base stat total of 414 between Generations VI and VII.
Masquerain seems to be based on a variety of insects. Although rarely shown, it apparently has the ability to walk on the surface of water using its wings as if they were legs, so it may be based on a water strider. Its Japanese name suggests inspiration from moths, many of which use eyespots to frighten would-be predators. Its habitat, translucent wings, and hovering flight pattern are reminiscent of dragonflies and damselflies. Its raindrop-shaped head resembles some lanternflies. Its mimicry of an angry face is similar to a mask or cat face.
Masquerain may be a combination of masquerade (a disguise) and rain.