Revert is a mechanic that is unique to the Beetles. It is the process by which units and structures change back into Harvesters. It is essentially morphing in reverse. Like most actions in Apex Predator, it can only be performed on ready cards.
To revert a card, remove all damage counters from it, place a new Harvester face-down underneath it, then engage both cards 1 turn. When the stack reaches the ready orientation, turn the Harvester face-up and discard the card that was reverting.
If a unit with a resource counter reverts, that resource counter can be given to the new Harvester.