Galactic Spiral Abyss

Description
The Galactic Spiral Abyss (Trench?) is a region of super/hyper compressed space created by the Anti-Spiral using his Death Spiral Machine. Inside this region Spiral power is drained from any user and converted into mass/energy making it even denser.

Throughout the aeons of wars between the Spiral races and the Anti-Spiral this place had become a graveyard filled with the endless remains of the defeated spiral warriors. For this reason the Anti-Spiral also calls this place the Spiral Graveyard.

Characteristics
This region behaves similarly to what we know as a supermassive black hole.

One of the similarities is that it has a density similar to water, therefore resembling a "dark ocean".

"The average density of a supermassive black hole (defined as the mass of the black hole divided by the volume within its Schwarzschild radius) can be less than the density of water in the case of some supermassive black holes. This is because the Schwarzschild radius is directly proportional to mass, while density is inversely proportional to the volume."

For example: ''"A black hole with the mass of 387 million of our suns would have the average density of water." ''(this doesn't take the volume of said black hole into consideration)

Also, just like a supermassive black hole, it has an extermely powerful gravitational pull and the pressure inside it is also tremendous.

"What happens when a black hole forms is that the effect of the gravity becomes so strong deep inside the matter that originally produces the black hole that no possible form of matter could possibly make enough pressure to resist the collapse anymore. So nothing does stop the collapse: the matter just continues collapsing more and more and more until it completely collapses into a singularity."

Apparently the Galactic Spiral Abyss has the mass of at least a whole galaxy worth of energy compactified. We know this for two reasons:
 * The first, and most obvious, is that the Anti-Spiral called it a "galactic" abyss, however this could also be a way of saying that all the spiral warriors from the galaxy ended up there so we can't take it as proof on its own.

order to get there they must have had a power close to what Simon had at the moment, otherwise it would've been impossible for them to reach the Anti-Spiral's universe. At the time Simon had a Spiral power comparable to at least billions of stars (calculated from the Arc-Gurren Lagann punch) so if each fallen warrior had that power drained from them then this region has a mass equivalent and perhaps even superior to that of a galaxy.
 * The second is that it had absorbed the power of countless fallen spiral warriors over the ages, and in

Anatomy of the G.S.A.
We can calculate the size and shape of the Galactic Spiral Abyss based on the data we have about it.

We can determine that it must have an spherical shape since that's the shape that any object as massive at this will have in space due to gravity, it is also the shape that supermassive black holes have, and the funnel-like shape showed on both sides of the Death Spiral Machine are also typically used to describe a black hole's region. After determining the shape of the G.S.A. it's easy to calculate its size by comparing it to the Ashtangas. In the scenes where they appear hovering over the G.S.A. the surface of it looks flat, this means that the sphere is close enough to appear flat (the same effect that makes Earth appear flat to us even though it's spherical).

By zooming in on the sphere we get to the point where the sphere looks flat and place the Ashtangas making sure their size is also consistent with the size of Super Galaxy Gurren Lagann (the Ashtangas are about the same size as Earth). The size of the G.S.A. is greater than our Sun.