It has been a few months now since Ren had stayed in the Mo Clan. During that time he taught Mo Feng the basics of the formless sword which drastically increased Mo Feng's skill with the sword.
After teaching Mo Feng the basics, Ren had also started training with his various incarnations. The first thing he learned was summoning techniques, one of his past incarnations even gave Ren all of his past summons. At the moment Ren had only summoned one being, and the very second the summoned being looked at Ren it actually started jumping around.
It turns out the beings that have a contract with the past incarnations were like Tsukiyomi. They can feel Ren's soul so no matter how much different he looks from his past incarnations they would always recognize him as their master.