In Beast Breaker, you play as Skipper Whiskersmith, a young mouse who grew up on a farm under the protection of their grandmother. They've been hiding from the rampaging Beasts their whole life. Until one day they receive a strange call for help from someone outside the farmhouse. Without missing a beat, Skipper grab Granny's old sword and runs to fight the Beast head on. Skipper is done hiding.

Follow Skipper as they answer calls for help from around the world, running to assist anyone in need. They meet many fellow critters along the way, all of whom have dealt with the rampaging Beasts in their own unique way. They also start to unearth the secret of the Beasts and start to piece together where they actually came from...