Though originally named RES, they were forced to rename after discovering an artist already called RES on iTunes. Their new name is a play on Gengar, one of the original Pokémon. Their debut album, A Dream Outside, was released on 15 June 2015. In October 2017 it was announced their second album, Where Wildness Grows, would be released on 9 March 2018.
After BBC Radio 1 DJ Huw Stephens played their first single, "Fill My Gums With Blood" on his radio show, the band were invited to perform at the Introducing stage at the 2014 Glastonbury Festival.