Known info about sectors 7, 18 and 19

These three sectors appear in a very similar, if not identical, form in the May 12 prototype, suggesting they were scrapped even before that build; it's possible, although unlikely, that sectors 7 and 18 never contained much of anything.

Known info and speculation about sectors 4 and 9

This part mixes objective facts and subjective speculation, speculations are not confirmed and should not be taken as facts.

Sector 4 used to contain the scrapped section that can be seen in the May 12 prototype, while sector 9 was probably a partial sector connecting sector 4 to another zone.

The original purpose of sector 4 can be confirmed by the September 29 prototype: in that build, sector 4 has already been stripped of all models and textures, but still contains collision data, and the location of it perfectly matches with the scrapped section; sector 9 also still contains collision data, but since the coordinates of it are unknown (and there are currently no tools to parse or visualize collision data) it's still unknown what it actually contains.

The theory of sector 9 containing a connection between sector 4 and somewhere else is supported by the fact that sector 3 calls for sector 9 to be loaded; this may seem unusual as sector 4 does not call for sector 9 to be loaded, but that could be explained in several ways:

• the reference was never there in the first place due to a mistake
• the reference might've been removed at one point (although it would be strange to have only one reference removed and keep all others)
• there might've been even more sectors after 9 that were completely deleted (but it too would be strange to delete some sectors and keep others)
• sector 9 connected to sector 4 through some sort of one-way path/passage, which means there wouldn't have been a need to keep sector 9 loaded as it was impossible to go back to it or even see it once inside (this is supported by the fact that in the May 12 prototype, the entrance to the scrapped section is one-way, and the whole section needs to be traversed to get out of it).

(the "strange" possibilities are more likely than one may think, as I have a strong impression, supported by multiple factors, that the game was rushed at the end of it's development for one reason or another, thus making "mistakes" and "slapdash" decisions more likely; the fact that these two sectors were emptied and not deleted entirely, and that they still contained collision data mere weeks before the final build of the game was compiled, also suggests that the decision to so was taken very late in development).

The fact that sector 4 calls for sector 8 to be loaded suggest that sector 8 also originally connected the scrapped section to somewhere else; this could've been done through the shell elevator and enclosed area that are present in the final build (with an extra passage that was then removed when the section was scrapped), but it's also possible that sector 8 originally contained something completely different and it then was reutilized for it's current purpose and the reference in sector 4 was never removed.

It is noteworthy that, in the May 12 prototype, the scrapped section is in the same sector as the outside area; however the level overall contains less sectors compared to the final release, pointing to the fact that some sections, including the scrapped one, were eventually moved to their own separate sectors (the whole level in the May 12 prototype appears to be one of the levels in the earliest phases of development, with plenty of missing or nonfunctional elements, earlier layouts, no Wolfuns in the whole level apart from Wolfun Frank, so it's possible that the split happened as the level continued to grow larger and more resource intensive) (in fact, the scrapped section in particular appears to be in an extremely early phase of development even compared to the rest of the level, with very primitive and placeholder geometry, no interactive elements at all apart from an Amortos and air cannon, which are the strictly required elements to enter and leave the section, and there are a bunch of weird elements consisting of a W with a circle around it, which I speculate were used as placeholders for Wolfuns).

Known info about sector 3

Unlike LEVEL_8, by the time the September 29 prototype was compiled, sector 3 had already been stripped of all models, textures and collision data.

In the May 12 prototype, the level consists of three sectors, with the inside of the fortress being contains in sector 3, while sector 2 contains a slide connecting sectors 1 and 3 (with the slide being very different compared to the final one, and strikingly similar to the one in LEVEL_13); notably in this prototype the level (mostly sector 1) also contains a lot of extra elements seemingly scattered around the level or misaligned with the rest of the level (both interactive elements, many of which appear to have had the surrounding level geometry removed, and level geometry making up small "rooms").

Ultimately, given the information we currently have access to, and not having access to any builds in between 12 May 2003 and 29 September 2003, no assertion about the original purpose of the now empty sector can be made.