Cold club
I didn't realize the Kido topic was here as well. :P
Create a forbidden Kido spell. You could include its level number, type, and an incantation.
Name: Infinite Overdrive (I'd like to have a translation, but I think Overdrive translated into Japanese IS Overdrive. So... Mugen no Overdrive? XD)
Incantation: Take the thread of control into thy hands. Unravel and set everything loose. Rise before the fallen. Glory before the damned. Spread before the scrunched. Lengthen before the coiled. Open before the closed. Red bow. Blue thread. Black box. Yellow light. White particle. Imbibe, compress, release and disrupt.
Effects: This Kido affects the user in the way that it extracts his innate powers and forcibly brings them out. The Kido raises the power by 10 - so that an unreleased shinigami who uses this Kido would roughly have the same potential as his normal bankai state. The reishi store that the user himself has is irrelevant because this Kido takes in the reishi of the surrounding and converts them into the user's own, much like how a Quincy's reishi absorption works. This Kido also enhances the user's physical capabilities (for sudden increase in spiritual power without the equal amount of increment in physical power will cause the user's body to be unable to take the strain) in the way that it enables the user to cope with the heightened amount of spiritual input and to increase the cells' capability of producing energy and replacing damaged cells.
Hayflick limit is not a problem here (since presumable a shinigami's cell physiology is different from a human... or a ninja)
What the Kido does is that it increases the speed, offense and defense of a shinigami tremendously. It enables the shinigami to reach into his powers even though he had previously no experience of them (e.g. bankai).. But obviously, those who haven't achieved bankai would not be adept enough to perform this spell in the first place. It also enables a shinigami who is skilled enough in reishi control to freely manipulate spiritual particles without actually absorbing them first, so you can suddenly make a Shakkaho appear behind an opponent, for example.
So basically, it's a combination of Tsunade's Creation Rebirth and Rock Lee's gates. Or Eon's bankai, but without the heightened amount of sensory input and enormous sense of pain.
Why the spell is forbidden: Obvious reason is obvious While the technique is dangerous if employed wrongly, the main reason behind the ban is because of the rate of reishi absorption of the technique. It is consumed in a rate such that the entire Soul Society would crumble into nothingness if a shinigami uses this technique for a period of even ten minutes. One could argue that the spiritrons in question doesn't really "go away" (conservation of energy and whatnot) but it would simply reduce everything into nothingness (the reishi that were once the roof of a building are now freely floating around). That's still a huge amount of damage though.
Though one doesn't really need to use this Kido to obliterate the universe... We know that /0 does tha- BOOM