Claiming is the act of taking telepathic control of a Sundered One. It requires training and willpower on the part of the human, and that training is one of the key purposes of the Academy.
Claiming is only possible because Powerful but broken creatures, enslaved to keep mankind aliv... More are what the humans call “broken;” something is very wrong with these creatures, and a human with steady, strong concentration can impose their will onto a Sundered.
If successful, a claim results in the Sundered One’s neural processes being connected to the human. The human can command the Sundered One to do anything; the only two limitations are the power of the particular Sundered (depending on tier) and the willpower and creativity of the human.
It should be noted that in time, the claimed Sundered One always dies – and that isn’t considered going wrong.