Green Crystal is a 1991 game by Compile. As best as I can tell, it came out in a compilation disk called Disc Station Magazine #32. It’s basically a Might and Magic like game on the MSX 2.
The fighting system is fairly basic. Enemies don’t have a lot of animation, and the game has a typical level of grind for this kind of game. There are handy icons showing you if you have weapons equipped. As best I can tell, the fights are purely attacks from the hero versus the enemy’s attacks. There doesn’t seem to be any magic unless if there are magic items to use in battle.
Plot wise, the game has a menu based talking system. Most lines of dialogue are fairly short. Django made an English translation, but it doesn’t seem to cover most dialogue, so the plot’s not that clear. The introduction has an eery sequence of a woman praying, a bleeding man, monsters over an image of an elf, and then some kind of floating demon with fire. Apparently, your hero is charged with fixing this.
The mazes are pretty tolerable for exploration in the early game. While you can get lost, it’s possible to find out where you are again. If I was willing to puzzle out the plot and do some mapping, I’m pretty sure I could finish the game. I suspect most people would not be interested in the game, due to the rough and non player friendly nature of the design.