DROD is a game that autistic people might enjoy while on methamphetamine. Its a turn-based, dungeon crawling puzzle-game. The way that works is: you can move in one of eight directions, you can wait, and you can turn your sword clockwise and counter-clockwise, and every time you execute one of those verbs, a turn passes. Every turn, other things in the tile-gridded room you're in will move, and every x amount of turns spawn units will create things that move. Thats pretty much DROD, "invented" (because it is so primally iconic a game design) by Eric Hermansen back in the 90s. Since then, it has expounded on that simplicity with so much manic variation that thousands of people have subscribed to Caravel Net and flooded its message boards with help requests, new content ("Holds" as it were) and all kinds of crystallized culture only possible in a hardcore gaming super-niche like the DROD series.
King Dugan's Dungeon was a fairly generic excuse to throw a lot of punishingly difficult dungeons at you (and that's coming from a guy named Patrick Dugan); Journey to Rooted Hold cultivated a plot and streamlined its delivery with well-paced and far better balanced level designs. Now, The City Beneath builds off the narrative and gameplay trappings of the previous two, delivering the mad challenge of KDD while measuring it with the balance and pacing of JtRH. If you like DROD, TCB will be like the indie equivalent of Guns of the Patriots, a well-produced extravaganza that vindicates its world with content.
The plot of TCB has to do with a vast subterranean civilization made up of personality-deprived "citizens". It's a goddamned empire, man, they've got control of international trade, manipulating kings and armies; they've got liaisons in every major government, thrones in their pocket. As Beethro, the Homer-Simpson-with-a-sword protagonist of the series, you're going to get to the bottom of this - literally. Like, the whole culmination of the game, and by extension the series so far, is to clear all rooms in a level, then proceed to a lower level. DROD breaks from this a bit, having you work your way through the underground city of that serves as this empire's seat, taking a detour or two to the surface (actually, its precisely two detours), but ultimately allowing you to reach "lowest point" which is exactly what it sounds like, the lowest point in the whole world.
When you get there, you take off a cover, and look down a hole, and everything becomes clear.
The gameplay stays fresh from level to level, keeping up with new, challenging variations. Many of these are handicaps -- the liability of pressure plates, the insane growth of the bramble, and god help you, the stubborn weak points of the gel. But then you find empowering additions, like the speed potion, which allows you to get two free moves for every move enemies make. If you've played JtRH, you'll know that a Slayer is a difficult thing to deal with, to the point where the climax of an entire game is structured around killing one. TCB makes you a Slayer of Slayers, and at times, allows you to best a whole crowd of them in hyper-kinetic melee. I'm talking about Bangkok brothel levels of fan service.
I think "Bangkok brothel levels of fan service" is a good way to end a review.