for them to hunt, they only need a piece of the flesh of their target/prey. It works the exact same way as a dog used to track/search for something (drugs/bomb materials) or someone (criminal/fugitive or a rescue mission).
as long as 1 of the 11 AFs survive, they can share their combat experience with the newly created 10 AFs back at Org HQs, making them much more deadly after each battle.
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do you remember, Audrey+Rachel vs Riful? and how the Ghosts had saved them?
now, is the time, to wonder why Audrey+Rachel were fighting Riful in the first place, hehe :D