If you are not familiar with the series (then you obviously have never met my brother..) it is a hack and slash style RPG based on the novels of Polish author Andrzej Sapkowski. The mobile adaption takes the role playing game- something difficult to perfect on a mobile device, and turns it into a MOBA- a more sympathetic genre for tablets and phones.
An adventure game set in the world of The Witcher, simply titled The Witcher Adventure Game. been announced and will be coming to Android. Developed by CD Projekt Red, the dev behind the Witcher games including the upcoming The Witcher 3: The Wild Hunt.