Delete the Virus

The bird finishes up the Fortress and very much closes it up, refusing access to whatever tries to go inside.
(2x) It then sets up a factory inside the fortress that constantly deposits small, weak, but annoying mites that will attempt to reduce the effectiveness of anything by swarming. They have 3 HP each, can do at most 2 damage per hit, and are produced 5 at a time. They will not be released from the Fortress unless a PV entity or player says so, to facilitate swarming. They exit the Fortress through a dog door.