Combining the procedural nature and character progression of roguelikes and the combat of a side scrolling beat 'em up, Abyss Odyssey feels like a watered down version of both rather than taking the best elements.
The dungeon crawling nature doesn't really combine well with the side scrolling aspect. The Abyss is split into short dungeon levels, pretty much all of which are a straight line left or right, go down a bit, then travel left and right again, rinse and repeat. Levels feature some minor outcrops of paths to take but rather than giving you multiple paths to the bottom they just serve as quick dead ends that usually have a chest or a weapon. Sometimes there's a wall or obstacle or can smash with the right weapon, but rather than being rewarded handsomely for finding these secret areas you'll just, again, find a chest or a weapon. Sometimes you’ll find the shopkeeper, who isn't in the least bit thankful for you rescuing him from his imprisonment.
The game is also extremely light on the "loot" aspect of dungeon crawlers, in fact most weapons you find are considerably worse than the stuff the guy at the beginning sells, and many times worse than the starting equipment. They also don't scale with your depth in the abyss, so you can find the best equipment you're going to find on the first floor of the dungeon. You can equip a few trinkets, each have effects like increased weapon damage or extra health, but you do so little damage per weapon strike that unless you find something that doubles your current attack it's incredibly difficult to notice any increases. You'll find money littering the stages which you can use to purchase stuff from the shopkeeper who has no problems getting around the abyss or at the start, before you enter the abyss, from the soldiers that just decided to set up shop rather than help out.
As such how good you are at the beat 'em up part is of far more importance. Sadly while the game does give you a brief tutorial during the prologue, it doesn't really prepare you for what's ahead. Combat is essentially a single button + one of four directions to perform a particular attack, characters also have skills, which are a second button + one of three directions, however which skill is performed can be set by the player at a shrine. At first glance combat can appear sluggish in that the delay between performing moves is quite noticeable, however you can "combo" moves to an extent to remove this delay. The combat basically comes down to crowd control, as if the enemies overwhelm you, that's basically it, they can juggle you can keep you from performing a single action all night long. Overall, controls are tight, but at the same time a bit too rigid, like the inability to change direction in mid-air, so if you press jump a bit too quickly and haven't turned around prior to the jump, you can find yourself jumping backwards into a wall you're trying to scale. This happens all too often for my liking.
You can unlock two further characters; Ghost Monk who just seems to unlock once you've played a bit and is much slower but hits far heavier, and Pincoya who you unlock by giving money to a fountain on a "gold stage", who is faster and whose attacks generally have a wider area of effect. You can also get the souls of your enemies, which allows you to switch to whichever soul you currently have, giving you the chance to play as almost (I believe there's a couple you can't) any enemy character. This touch adds a lot of strategy as this soul has its own health meter in addition to its own attacks, so finding the most appropriate soul for your play style or switching between that and your character at an opportune time can help a lot in battles.
Where the game shines is in its aesthetics, the game looks amazing and while it suffers from generic dungeon settings (fire/ice/forest with no real logic connecting them), each environment has some traps and obstacles that are unique to them.
However the story feels just tacked on, you're given the bare bones of the premise as justification for you to continue your descent into the Abyss. Sometimes enemies will drop "journal pages", which are the warlock's secret diary that he tore up and distribute amongst his minions... for some reason. This journal is where you find out pretty much all of the story and backstory... If you get lucky enough for the game to drop it, I'm still missing a single page about 10 hours after picking up my last entry...
It isn't exactly difficult to get to the end of the abyss, but it'll most likely take a few attempts to beat the warlock since his attacks are hard hitting and don't require him to be near you (he can also spam moves like crazy). They included some kind of community driven goal in that the emblem on the front of the book as the game loads will gradually break, revealing a new emblem once the old one is completely destroyed. This indicates that the dungeon enemies are different; however whether this means they're outright stronger it was hard to tell. The levels also seemed slightly longer, however it doesn't seem possible to go back to the "original" version of the game to compare.
The game *is* fun, which I guess is the most important factor, but it comes with the caveat that it relies more on the enjoyment of beat 'em ups than dungeon crawling. Also that each subsequent time through the dungeon becomes less fun since there really is nothing to explore. The game may change each time the emblem shatters, but if you're not actively checking the game for that, you may never know that it's updated, nor really care.