From Kamen-Rider Gaim.

Elementary Inves: 初級インベス:
The Elementary Inves are action figured-sized Inves summoned by Lockseeds from the Helheim Forest during an Inves Game to battle against the Armored Riders (opponent) or the opponents' Inves.

they break out of an Inves Game, they will go into a rampage and start attacking until they are sent back into the Helheim Forest. When they eat Lockseeds, they will evolve into a stronger, animal-based form called Berserker State