Curse of Darkness is an improvement over Lament of Innocence in many aspects, and makes for a pretty fun experience.
The story takes place three years after Castlevania III: Dracula's Curse for the NES. Dracula may be dead, but the curse he left behind lingers throughout the land. You're filling the shoes of a Devil Forgemaster named Hector; a man who was once a loyal servant of Dracula until moral implications forced him to give up his potentially evil privileges as one who can command powerful demons called Innocent Devils. He seeks revenge against fellow Devil Forgemaster Isaac, an insane lunatic clearly a few cherries short of a parfait, who orchestrates a mock witch trial that results in the brutal death of Hector's beloved. But the story stretches far beyond a simple quest of revenge. With Dracula's curse soiling the peaceful Transylvanian countryside, you must reignite your powers as a Forgemaster and use Innocent Devils to stop Isaac and set things right again.
As I stated earlier, the game improves greatly upon Lament of Innocence. You're now able to equip different weapons such as swords, axes, halberds, (even a guitar!) to deal with enemies, the game world is much larger is scale, and you have much more liberal control of the game camera. Furthermore, you benefit from the help of Innocent Devils--demon allies you'll find throughout your journey whom act as a second character that you can develop into different creature types that suit a given situation. In a pinch, Innocent Devils are exceptional assets. Against difficult bosses, you'll be surprised as how effective they can be depending on how you've developed them.
As huge as the game world is, it suffers from the unfortunate demerit of repetition. Basically, you'll find yourself wandering through endless hallways that are carbon-copies of corridors you passed through just seconds before. Never mind the fact that the visual style of the game is beautifully rendered in a dark, foreboding and sinister atmosphere as is custom of the franchise. While there's nothing wrong with the graphics, it might have been better if the environments were as varied as the monsters, because many times the player might end up feeling disoriented when exploring these vast areas--oftimes referring to the map when they feel they're lost. Still, you can't go wrong with how wonderfully dark and evil your surroundings are.
The music by Michiru Yamane is simply gorgeous. She's come a long way since Bloodlines, and the orchestrations are as immersive as ever. Not too fond of the ending song, but her other compositions more than make up for it. Another strong aspect of the game is the voice-acting during cutscenes. They are among the best I've heard in a game--wonderfully delivered in every sense of the term and a joy to watch over and over again--would that there had been an option to replay movies!
Overall, Curse of Darkness makes significant improvements over Lament of Innonence and, in many instances, is an admirable attempt in bringing the series to 3D--not the best, but a good one. Castlevania fans may want to give the game a chance if only to enjoy the story that happened after Dracula's Curse (not to mention the fact that Trevor Belmont makes a cameo). It may not change a lot of minds, but Curse of Darkness is certainly a fun endeavor.