UAC constructed a bolt-hole on the dark side of the moon which was terraformed for the purpose. It was known as the Waterwheel because of its shape. When you completed the cleanup at Deimos you were warped to the Waterwheel because the infestation had spread even there. You find yourself transported to the centre of the Waterwheel and need to find your way to the exit warp-point cleaning up as you go.
Sadly, the hell spawn has already carved holes into the roof and the upper levels have been flooded. Fortunately, door blocks have prevented the flooding from spreading to the control rooms that make up the wheel(s) and the lower levels where the bugs from hell have constructed their dead-rooms.
It's a very impressive megawad with a nice themed ancient Egypt atmosphere, with very nice choosing of textures to contribute to that theme, very nice architecture and impressive (and very risky) twist on the story going from ancient Egypt to alien spaceships, without using hi-pitched colors like in Ancient Aliens.
Also, very tough megawad, if you're masochist enough, you can play it with Complex Doom and add LCA for more doses of pain.
It's okay. Quite easy due to the abundance of artifacts, mana, & health. The level design is fine, nothing special. The only truly bad part was the unmarked puzzle bookcases, forcing you to wallhump the entire library as a last resort. Otherwise it's pretty simple stuff, running around finding keys and smashing monsters. The texturing and lighting aren't fantastic but aren't noticeably bad either. The only glaring issue is that many windows just show a wall textured with the sky texture rather than an area with a sky ceiling. Yet there are perfectly normal outdoor areas. Perhaps the author only figured it out skies halfway through development?
Anyways, this is worth your time if you want an hour or two of simple Hexen fun.
It's a nice wad overall, nice map design, textures and monster placement, enjoyed playing on D-Touch (GZDoom1.8) with Dude4th weapon mod. My only complain would be the secrets, they have very few to no clues about their position. There was a problem on E3M5 on the secrets around the squared starting room with stairs, the wall closes and let me stuck inside, had to use idclip to get out from those secret rooms.
I recently played through this continuously twice on UV. Overall I feel this is an expertly crafted WAD from start to finish. Beautiful scenery, great soundtrack, and intense gameplay. Maybe a little too intense sometimes, and with that it's probably not a WAD I'll recommend to newbies. If less experienced players absolutely have to try it, I suggest playing on the lower difficulty modes as the included readme suggests. Describing the later maps of this WAD as "brutal" on UV is an understatement to say the least.