Here's a list
Basically they're modules. Necromancer Games printed a bunch of them for 3rd edition, and the ones that I got were good reads (interesting examples of design). HOWEVER, iirc, there was a dispute of some kind between the author and the Necromancer guys: the last module(s) were never printed, despite the whole "1-4" thing.
Maze #1: the PCs are stuck in a maze of traps, but Rogues are not allowed (ie: figure out the traps without disable device). The background of the story is they're supposed to go kill the King, but the court wizard zaps them into a magical trap-filled maze.
Maze #2: Still in the Maze, but now the PCs are inside a Demiplane-trap inside the maze where they have to solve the demiplane in order to leave them, and thus leave the maze. Maze inside the maze. Still no rogues. Theoretically this is part of maze #1, but they gave it its own book.
Maze #3: Oddly decided to print the prequel 3rd, the PCs are sent to kill the king (who's an evil clone imposter) by sneaking into his Tower/castle. The tower is detailed, along with a chart for keeping track of the movements of NPCs in the tower: whatever time of day the PCs show up, NPC X is in room Y. However, if you complete the adventure, the PCs are zapped into the start of Maze #1. What *really* doesn't make sense is that in this adventure YOU CAN PLAY A ROGUE!!! So... why can't you play one in the next two modules if you could in this one?!*
After that, the author and Necromancer Games didn't see eye-to-eye (this is a rumor, so don't quote me), and the last module didn't get published.
I don't know that the above deal is worth it, but it may be. It's 1e, though, so if you like d20, get d20.
*I'm not 100%, but maybe the original module came out before Thieves/trapfinders did in D&D? Or at least the idea of a rogue takes away from the fun of this somehow? Personally I can't imagine that a rogue can just poof away traps without a logical reason for it. it's not like they can get to all the gears and/or spells in all cases: if a door is bolted shut, and the doorframe is shaped so I can't lift the bolt with sliver of metal or a coathanger, I can't "disable the device". "you see three levers beneath a statue of a dragon's head" doesn't mean the PCs can meld through stone and take apart the mechanism of the dragon trap.
Oh well.
