The 
Rewarp staff allows the user to warp themselves to other places on the map. This staff is very common among enemy Dark Mages in Fire Emblem: Thracia 776, it is very useful to either steal the staff off an enemy or capture them and take it off them and then give it to your own staff-users as it can be extremely useful. In Fire Emblem: Radiant Dawn, it is wielded by several Magic users throught out the game the party must fight, including but not limited to: Izuka, Lekain, and Sephiran.
Enemies using this staff can be very frustrating, since they can not only warp to attack your unprotected units, but can also rewarp to escape when they are surrounded. However, they tend to use it rarely, due to the low amount of uses.