007: License to Spell DooM (007LTSD.WAD)

Stephen Clark was something of a self-appointed vanilla advocate, a dude believed that OG Doom and Doom II were capable of great things that could close some of the gap between them and Quake and subsequent FPS games. He made Operation: Lightning, a Doom II episode that deliberately evoked Quake II with its dropships and had carefully arranged vanilla sector machinery to create effects like exploding reactors, flooding vessels, and collapsing bases. Then he took his lessons learned and authored Fragport, a 2001 "21st Century Doom 2 Episode" that was actually a megaWAD and which toned down some of OP-LITE2's worst excesses. Then he pushed Heretic into uncomfortably ingenious places with the Shadowcaster episode in 2002. This is also the year where he learned to stop worrying and love the ZDoom. Enter 007: License to Spell DooM, an E4 replacement for The Ultimate Doom.

Shadowcaster (SHADOW.WAD)

From 2000 to 2002, Stephen Clark (aka The Ultimate DooMer) had created an episode for the original Doom and then converted it to Doom II (Operation: Lightning) and crafted his epic, 21st-century Doom II megaWAD (Fragport). His next target for his own brand of experimentation and modernization was everyone's favorite Doom clone, Heretic. Shadowcaster is an episode 5 replacement for Shadows of the Serpent Riders, released in September of 2002. I'm not up on my Raven Software lore but I don't think that there were any major engine changes between the original release and the free expansion that would have necessitated using the E5 slot. Presumably, this was more of an aesthetic decision where the author could avoid having to contend with a clashing intermission screen.

Operation: Lightning (OP-LITE2.WAD)

Stephen Clark, aka The Ultimate Doomer, made his debut splash in 2001 with his solo megaWAD, Fragport, but he had previously made an eight-map Doom episode called Operation: Lightning. Somewhere down the line he converted it to Doom II and added three more levels. While it was finished mid-2000, Clark didn't publish it until early 2002, once he saw some positive feedback for Fragport. OP-LITE2 replaces MAP01-MAP12 with the final map merely being an episode bumper to keep you from coasting into the regular Doom II campaign. It is as far as I know vanilla-compatible and should function correctly in the source port of your choice.

Fragport (FRAGPORT.WAD)

Stephen Clark. Newstuff reviewer, ZDoom guru, The Ultimate Doomer. All of Clark's critical successes - 007: License to Spell Doom, Super Sonic Doom, and Serpent: Resurrection - were ZDoom releases. Fragport, his debut, is a little different. Conceived for vanilla Doom II, Stephen tried to leverage as many tricks as he could think of in order to show just how hard the original executable could cook. Sure, some suspension of disbelief is required, but that is generally the nature of the beast when it comes to doing anything complex in DOOM2.EXE. Fragport was originally released in 2001 and it is a full game replacement. I've seen it passed around the internet as BOOMSKY, much to my confusion. In the absence of any clarifying information I would stick to the official version found on /idgames.