luck: It helps user to obtain better euqipment from the blackmarket store, and helps anything that has to do with luck including upgrade/ stat transfer

Fehu: it is rune. You can upgrade rune with slate stone that can be purchased from the medal store. if user place rune into the socket it increase the luck points. If user upgrade rune into Jera (top class rune) user can upgrade normal gem into perfect gem to place into the equipment. (need ability level 3 to make perfect gem)

so luck also affecting upgrade and stat transfer?