Solid Dungeon Crawler
It really helps to know the rules of 2nd Edition AD&D when you play this game. I supposed you do not need to know the rules, but personally I like knowing whats happening and why. I like knowing what my stats give me for bonus', and exactly what AC and THAC0 are, how much damage the weapons I am using will do, and who should really be using what weapon, when and where.
That said, you don't NEED to know the rules. It just helps a lot with understanding the game.
It helps to have a guide, or its easy to get lost in this game... it is also possible to completely screw yourself in this game, to the point where you have to start over, simply because you used a gem in the wrong spot, or possibly a key. I'm not even lying.
I played the this version (snes) when I was younger, and was never able to finish it... we actually thought it was broken, and unfinishable.