Please help identify (mega)WAD

Hi all,

some 8 years ago I played a Doom 2 WAD or megaWAD and for some reason, I remembered it recently and I want to play it again. Now the trouble is I don't remember its name. I went through all classic megawads (Memento Mori, Hell Revealed, Evilution, Plutonia Experiment etc) but none of them is the one I'm looking for. Here is rough description of what I seek:

As far as I can tell, the (mega)WAD had some story containing time travel. Indeed, one of the levels contain a "time portal", which was in reality a cube with dimension of roughly 256x256x256 units. The time portal had to be activated by four buttons near its sides and I think one needed to find all three keys in order to activate it. After the "time portal" level, the levels got really huge. Usually some kind of a cathedral or a castle in the middle of "ocean", with lots of sniper monsters. One characteristics I distincly remeber that the levels could be extremely annoying at times - one could spend hours looking for a missed button. Considering that the levels were practically a maze of chambers, courtyards and buildings interconnected by complicated set of corridors, it was fairly easy to overlook something. Even so, the levels were still compatible with original Doom 2 executable with all its limitations.

Now I understand that this description is pretty vague but I'm unable to describe it any better, even though still I remeber a few levels vividly - Doom simply does not allow for too much unique environments and I could easily mislead you. In any case, thanks in advance for any tips!

Sounds like Eternal Doom III.

(Verify with screenshots.)

The castle-in-the-ocean you remember may be Map12, especially if you also remember starting in a little wooden shack.

Yes, this looks like it! However, I tried Eternal Doom III on Zdoom and I must say, it now looks a LOT different than I remeber... Weren't the levels re-used and/or modified in some other megawad, by any chance?

In any case, thank you very much!

From what I understand, it's had multiple releases. They identify the different versions near the bottom of the "Eternal Doom III" link, and I think I might have played the original 13-map release very very long ago because when I went to "revisit" Eternal (which was only very long ago) and downloaded the 32-map final release, some of the maps that I recognized seemed to have had some revisions and upgrades done, most notably map01.

It's also possible that somebody could have used them to do their own modified versions, but I'm pretty sure that's against the release policy and any maps that did that wouldn't be available on the /idgames archive.