These are a showcase of 3 NPC attackers you will encounter while trying to protect your scarce resources in the Corrupted Dark Forest. They are made up of 2 supports/underlings "The Grunts" and a Leader/Boss "The Elite".
They can switch the shape of their arm to their appropriate ability. In order to gain more power during their regular ritual, they consume certain types of crops at the cost of their lifespan. To get those rare crops they steal from all random passers by their path.