Promethium is a rare element found in Ben Tennyson's universe.
History[]
Hero Times Two[]
Black Knight sent The Pack to retrieve this nanite-free material to be used by Providence to travel in time. Rex hunted the Pack to Ben's universe and teamed up with Ben, Gwen and Kevin to stop the Pack. However, the Pack was able to obtain the element from a laboratory in Japan and returned to their own universe.[1]