It's pretty vague and complicated, so here's the rundown. Loot the body near the artifact first to get the medallion and six of the seven tablets. Go towards the back of the cave and you should get a message about something watching you. Wave the medallion around and defeat the stoneray that attacks you. Loot it to get the gem, then go into Mission Items and use the gem to put it back in the medallion. Then go outside the cave and west until you reach an altar with an object on it called Relic Keeper's... something. I don't quite remember, but interact with it and a Massassi Relic Keeper should attack you. Loot it to get the Tablet of Victory, then go back to the artifact and put the tablets in this order: Passion, Strength, Power, Victory, Broken Chains (the Sith code, pretty much). Finally, touch the completed medallion to the artifact, and boom, puzzle solved.