Ohh thx for the clarification

My question was how did they transfert things between the realms

In that scene wu talks very hardly I would guess that ras imprisoned him and drained his energy (like he want to do with the source dragons to inverse the merge)since he is the elemental master of creation which i would guess have a lot of energy like the golden power

Wu appeared in a spiritual way maybe by meditation leaving his body to guide the ninjas
But why are you sure that ras did not imprisoned him .