Museigen nota jōtai

"Dammit! I don't know what happened. When I felt that bitch Natsu's soul, there was nothing there, and then I fell into this feeling of despair. I blanked out after that...sort of. I mean, I was there, but I wasn't! I just felt emptiness; mine and hers..."

- Chireru to Noire Amakuni, after their second encounter with Natsu

Museigen nota jōtai (無制限のた状態, Unlimited state) is a form that is the manifestation of the unyielding power of emptiness staining ones soul. It symbolizes a wound in the spiritual existence that is maintained by the lynchpin, the Soul King, though the Soul King itself is not effected. This is because the a soul stained by emptiness no longer counts as part of the equilibrium between Soul Society and the world of the Living, and is percieved as a "threat" by the Soul King, regardless of its disposition.

Overview
For Humans and Quincies, the form it takes is dependent on the reason their soul is stained in the first place( though it is possible for certain Shinigami to utilize this form like this). However, for Shinigami, Arrancars and Kaiju-Ningen, it "melds" with their respective releases, creating inverse variations of their releases. Initially, the form is accessed by intense negative emotion (for Chireru, despair is required for his unconscious "Museigun nota jotai"),though the form itself is characterized only through the individual's eye's and not in its "true" form, though this is dangerous because they can "inject" emptiness unto another individual if left unchecked, potentially staining their soul as well.

"True" Musei nota jotai
Those who gain a foothold on their inner emptiness can access their Museigen nota jōtai forms. This form is unique for Shinigami and Arrancar in that it merges with their respective Bankai or Resurrecion when mastered( in Natsu's case, it fused with her Teiki-teki kemono no katachi (定期的獣の形, Recurring Beast Form), though such a fusion is optional and the original Bankai/Resurrecion can still be accessed. however, the form is hard to mantain. Using the form anylonger than 15 minutes runs the risk of an automatic Soul Suicide, depending on one's endurance. Access to this form allows for:

Enhanced Spiritual Pressure: This form is capable of a massive increase of potential spiritual pressure, as well as it becoming denser than in an average state.

Kūkyo shahei(空虚遮蔽, Emptiness Shield): A dense spiritual energy armor materializes, further increasing defensive capable far beyond what normal Blut or Hierro could provide. In some cases, the defensive powers are further increased rather than gain the spiritual energy that accompanies the form, as in Tazuma's case.