Thread:Zf6hellion/@comment-5778280-20141122215105/@comment-1493741-20141127034731

Essentially the idea is that a Jiukundao is a crystallization of an event (A person's death, most commonly). As a result of it, that person's soul is stuck in a form of stasis and it cannot be changed from that point on unless the person dies or the Jiukundao is destroyed (A process available only to the Soul King). As a Zanpakutou constitutes splitting ones soul, which would be a form of change, one cannot have both.