Board Thread:Questions and Answers/@comment-5239435-20130206201307/@comment-4957813-20130209150534

The Shinigami's personality and behavior starts affecting the Asauchi's behavior. Since a Zankpakuto is created by a Shinigami's soul and personality, the Asauchi starts becoming the reflection of some part of the Shinigami. For example, Shuhei's Zanpakuto, Kazeshini, is a chaotic Zanpakuto because Shuhei surpressed his intense urge to kill and destroy. This urge, because it was so great, was imprinted on to the Asauchi he received and thus Kazeshini was born. You can't make the same Zanpakuto if the soul is completely different.