D&D item: Martyr’s Collar

Seeing how everyone else is currently creating interesting items, I thought that I should throw one of my ideas into the mix. And after a bit of tinkering with how it should work, I present:

Martyr’s Collar Level 5

Resting tight against the throat, the wearer is always reminded of the price of sacrifice.

Lv 5   1.000 gp

Item slot:
Neck
Property:
This item can mean instant death for the character. To wield it, the character must succeed at a hard willpower check. After three failures, the character needs to take an extended rest before trying again.
Power (At-Will ♦ Necrotic):
Standard action. A conscious and willing character may activate the collar while it is around their throat. The collar magically constricts, severing the user’s head from their body. The user’s life energy serves as a power source for the collar and sends every attuned ally in range (burst 10) to the point defined by the attuning process.
Being able to survive the decapitation does not save the user, as all of their life energy is used up to power the collar’s magic.
The allies do not need to be willing, conscious, or even alive. If, for whatever reason, the destination is not reachable, the collar will not activate. After the teleportation, the collar expands to its normal proportions and loses any attunement.
Power (Daily):
Standard action. Every willing ally in a burst 5 are attuned to the collar, and the item itself is attuned to the location. When the at-will power is used, all allies attuned and in range are transported back to the current location. The collar does not need to be worn to be attuned; any character touching the item can initiate the process. When passing between owners, the item does not lose connection to any attuned user or the attuned location.

Nobody really knows how these devices ever came to be, but they seem to have been used by devout and loyal warriors throughout time to save comrades from certain death by using their own life to shield them. The ultimate heroic sacrifice, most souls sacrificing their bodies this way ascend to the Astral Sea.