Here is some rules- since I got beat to the answer!
Autonomous
This equipment is attached to a creature, and functions independently from that
creature. It does not take up an equipment location. It is unaffected by, and cannot
be modified by; traits, abilities, or conditions of the creature it is attached to.
However, it can be affected by other sources and objects.
If the equipment provides an attack, that attack may be used once per round,
as a free action, at the end of the creature’s Action Phase. If the attack is a melee
attack, it must follow the normal rules for guarding; however, it will not trigger a
counterstrike or damage barrier, and will not remove a guard marker from its target.
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And yeah- Marked for Death says "Creatures"