User blog comment:Apocaylpse06/Ichigo Kurosaki's (New) Zanpakuto/@comment-5090141-20120508220555

no its not engetsu because if you remember right not long ago isshin kurosaki fought with aizen in the fake karakura town which is pretty current after ichigo got his shinigami powers back so that proves that theory that thats why isshin didnt have his powers for the past 20 years wrong. besides isshin didnt lose his powers as a shinigami he just came to the human world and quit being one. but see what happened was ichigo was only a substitute shinigami which means once his powers were taken he nolonger was one but the glowing sword you mentioned was made up of everyone else's rietsu so because each zanpakuto is matched with is user perfectly zangetsu was still a living soul as all zanpakuto are spiritually it was matched with ichigo again but i believe all the rietsu from everyone else fused in with ichigos so we got a change in its shikai state