Would Shen use his spirit sword or physical sword
When he fight an undead from the shadow isle?
When he fight an undead from the shadow isle?
The undeads of the shadow isles are ghosts which seem to be a type of spirit themselves,so he'd use his spirit sword against them.
Spirit, probably. Only certain weapons, like those made of silver or are magical, can damage beings from the Shadow Isles (Lucian's guns, Vayne's bolts, etc.). He uses a steel sword, so he would use his spirit sword to deal with the trapped souls in the Mist.