Enchanted artifacts given to ACEs on assignment. The rings allow for instantaneous teleportation back to the Academy to take care of outside business.
ACEs are able to use the signet rings to rejoin their party once outside business has been resolved. ACEs teleporting back into the field assignment are placed adjacent to another member of their party, who will then update them on current situations.
Abuse of the rings as a means of escape or refreshment results in expulsion from the Academy.