Custom DirectX/GS Midi for a title that I'll probably never finish. :(
The relics are ancient gates between the 'Ruined World' and the 'True World', locked to but a few. The protagonist first discovers one just after (and as a direct result of) the tutorial fight (see : Mine Crush), and it's the events that occur on the other side that set the story going.
Relics themselves are essentially hemispherical rooms built underground in tectonically stable areas - their lack of accessibility is exploited by the True Worlds inhabitants to prevent the monsters of the ruined world crossing over, and known relics are normally well guarded.