Dark Earth is one of those great underappreciated games that goes largely unnoticed
It came out rather quietly in 1997 with next to no one really picking it up. Well this reviewer did all those years back and it was a lot of fun and it still is to this day.
Gameplay - It's pretty typical Action Adventure like although the way you do combat is quite nifty. Instead of simply pressing one button to do your attacks, you have to go into combat mode and hit a combination of keys to attack (this is also how you pull off combos). It was a great system that unfortunately has not yet been put to use again in terms of PC Action Adventure games.
Plot - Basically, your Arkhan. A man who finds himself poisoned with an evil poison. It's eating away at not only his body but his very soul and unless he finds a cure, he will become the very thing he hates. Basically, most of his quest takes place within the last remaining place of light on this Dark Earth. Theres also another plot that makes up most of the game but for some reason it feels more like a sub-plot. It's about the enemies getting closer, the light getting weaker and you having to find a way to stop them.
Graphics - They pale in comparsion to today's games. But for 1997, these were pretty awesome graphics. All the enviroments and characters are very uniquely designed as well.
Sound - Solid voice acting through out but the music leaves a little to be desired but other than that, great stuff!
Basically, if your looking for a great 3D Action/Adventure game with a unique story and great characters, I would definately recommend Dark Earth to you. You'll probably be able to find it somewhere for a good price these days and it's well worth it.