It's tempting to reflexively call Dragon Warrior Monsters a "Pokemon clone." It came out on the Game Boy hot on the heels of Pokemon's success, and the general theme is capturing and training monsters. It really plays nothing like Pokemon at all, however; it stays much more true to traditional Dragon Warrior / Quest aesthetics and gameplay. The end result feels much more like a Dragon Quest side adventure than Pokemon with Slimes and Drakees and such slapped in.
DW Monsters is actually more like a fusion of two concepts that Armor Project had already developed long before Pokiemans was even a twinkle in Shigeru Miyamoto's eye. It basically takes the optional monster training character class found in the SNES Dragon Quest games and expands it to a full game, blending in a little bit of the roguelike randomized dungeon style of the Fushigi no Dungeon series (Taloon's Quest
, Shiren the Wanderer
). You can actually trace the concept of monster AI battles all the way back to the monster fights you could wager on starting with Dragon Warrior II!
Anyway, the setup is that you play as young boy Terry, who is just peacefully sleeping at home one night when a creepy monster jumps out of his sock drawer and kidnaps his little sister, dragging her off to Dragon Warrior World. A slightly less creepy monster quickly follows and also abducts Terry, taking him to a kingdom in a giant tree, where the King tells him that there's no point in looking for his sister because if he simply goes from not even knowing where he is to becoming the greatest monster trainer in all the land, he'll get a wish that he can use to bring his sister back. OK then.
So with that flimsy setup we're off to the Giant Tree, which is kinda like Dragon Quest VII in that it's a central hub world from which you go to all sorts of disassociated smaller worlds through Traveler's Gates. The main overarching goal is to work your way through the ranks of monster trainers by winning in the Arena, which is conveniently located in the center of the tree. However, to do that, you'll need to find and open up various Traveler's Gates throughout the tree kingdom, which take you to little mini-worlds in which you catch new monsters and level-grind.
The little mini-worlds through the Travelers Gates are where the roguelike element comes in. Each one is composed of a few randomized floors with randomized treasures scattered about; you proceed by finding a hole to drop through to the next floor. Sometimes, between floors, there will randomly be a chapel for healing / revival, an item shop, or a save point. You can also find Warp Wings to bail you out of the mini-world before completing it. Death kicks you back to the Tree with your items stripped and half your gold, except for the stuff you stashed in the Vault beforehand.
Each world ends with a boss battle taken from some previous game in the series; for example, the first gate has you fight the dragon you rescue the princess from about midway through Dragon Warrior I. These boss monsters are then recruited into your party upon defeat; monsters in random encounters may also decide to join you when beaten, and the odds of this are improved by tossing them various tasty meat snacks while you're fighting.
Battles are pretty much the stock Dragon Quest engine, except that you can give each of your monsters a general command (Charge / Mixed / Cautious) and let their AI decide exactly what to do. You can give them direct and specific commands in battles outside of the Arena, including boss battles. However, it's important to train them by using the general commands while in the Traveler's Gates, as they have an unseen level of response to each command that goes up as it is used, and if it is too low they may refuse to act in the tougher Arena battles.
The real meat of the game is in the breeding system, however. After completing the first few Travelers Gates, the King allows you access to the creepy old breeding wizard. Every monster has a gender, and any male can be mated with any female to produce offspring that has mixed qualities. You pick the one you want to be the pedigree, which will be their base category of monster, and then they inherit some abilities, buffs and stat boosts from the other parent. So for example, if you use a dragon family monster as the pedigree, you'll get another dragon type like the Drakee or DragonKid, but with some added abilities from the other parent that they don't normally have.
Unfortunately, DW Monsters is one of those games that had a shorter shelf life than most. It was better when translucent purple Game Boy Colors ruled the playgrounds and kids were toting it to school with their link cables to battle and breed their monsters. Without multiplayer, you're stuck with pretty much nothing but repetitive grinding in samey Travelers Gates worlds. The first few floors of each Gate are basically identical and seem to draw from an identical set of random floors, the only difference is what treasures and monsters will appear. They don't get any individual personality until the bottom two or three floors, where a tune from an old Dragon Quest game (plus maybe a slightly altered tileset) kicks in. The little vignettes with the bosses of each Gate can be interesting / funny for longtime fans of the series, but that's about it. There's no real ongoing story to speak of.
If I were grading on technical merits alone DW Monsters would have to get a 4, maybe even a 5/5. Armor Project really did this one up as if it were a console game, complete with a new score by Koichi Sugiyama (though fleshed out with some songs from previous games). Unfortunately, that's not all there is to it. Multiplayer is functionally dead, and the solo player experience doesn't take long to get repetitive and tedious. Big fans of Dragon Quest will still likely want to give it a look just because of the concept and production values, but don't expect a sprawling open-world quest in standard DQ style.