From Bulbapedia, the community-driven Pokémon encyclopedia.
Hydreigon has been featured on 4 different cards since it debuted in the Noble Victories expansion of the Pokémon Trading Card Game. Hydreigon cards are normally Darkness-type or Dragon-type Stage 2 Pokémon. In Japan, Hydreigon was featured in the Hydreigon Half Deck released in March 2012.
List of Pokémon cards featuring Hydreigon