Gardevoir is a Psychic/Fairy type Pokémon that is the final evolution of Ralts.
The most expensive version of Gardevoir in the Pokemon TCG is the Dark Explorers Secret Rare.
In Unbroken Bonds, Gardevoir was featured as a Tag Team with Sylveon. Most players would consider this the most popular version of Gardevoir found in the Pokemon TCG. The Gardevoir/Sylveon GX Tag Team is also available in full art and both versions are available as rainbow rares.
Gardevoir evolves from Kirlia, who evolves from Ralts.
Kirlia can also evolve into Gallade.
Description from Bulbapedia:
Gardevoir is a bipedal, humanoid Pokémon whose body resembles a flowing gown. Most of its body is white, but its hair, arms, and the underside of its gown are green. Its hair curls over its face and down the sides of its head. Behind its red eyes are short spikes, resembling a masquerade mask. It has long arms with three fingers on each hand and slender white legs. A red, fin-like horn extends from its chest, and a shorter, more rounded horn extends from the back. A band of green on its chest extends to the center of the front horn and connects to its sleeve-like arms.
As Mega Gardevoir, it turns almost completely white; only its hair remains green. Its gown becomes longer and wider, resembling a bridal gown. The forearms are slightly thicker with a pointed extension above the elbow, resembling gloves. Its facial spikes are larger and now curl upwards. In contrast, its hair is now shorter and more tightly curled. There are now two horns in the center of its chest, extending to either side. These horns are said to be a physical manifestation of this Pokémon's heart, and it is able to use tremendous psychic power now that it is open.
Gardevoir is able to see the future using its psychic powers. Additionally, it is able to create small black holes, distort dimensions, and support itself without feeling the pull of gravity. Its power reaches its peak when protecting its Trainer, whom it will protect with its life. This Pokémon inhabits urban areas.