Mugetsu

Being in this form allows Ichigo to use Mugetsu.[3] Once it is used, the transformation dissipates. Afterwards, he will lose consciousness, accompanied by intense pain, with the loss of his Shinigami powers following. Any remaining Reiryoku will stabilize, and he will awaken some time later (roughly a month), followed shortly by the loss of his remaining Reiryoku.[4] However, when Ichigo lost his Reiryoku, a tiny portion of it accumulated in a single location inside of him over time,[5] and he began to regain it slightly after a year and a half.[6]
 * Mugetsu (無月, Moonless Sky): Generating a blade of deep black Reiatsu in his hand, Ichigo swings it towards his target. Doing so causes a massive veil of black Reiatsu to erupt upwards and approach the target, darkening the sky and heavily damaging anything caught within the blast.[7][8] Afterwards, the energy continues to rise before dissipating into the sky.[9] The technique is strong enough to severely damage Sosuke Aizen in his strongest evolutionary stage and force him to regenerate at a previous stage.[10]