Here are the basics of the relics. Go out and get them.
Each realm has two relics at this time. One adds a bonus to melee damage potential, one adds a bonus to magical damage potential. Each of your relics, while safely nestled in its shrine, grants a 10% bonus to damage in player vs. player combat (the default). If you control an enemy relic, it will grant a 10% bonus to damage for PVP and PVE.
Unless you control your own relic, you cannot go steal an enemy's relic of that type. That is to say, if you don't have your melee relic, you must first steal it back before you go after your enemy's melee relic.
You cannot ever move a relic (either yours or your enemy's) from your homeland's relic shrine. You can only pick up a relic (both yours and your enemy's) from an enemy relic shrine. Once you have stolen an enemy's relic, it needs to go to the corresponding shrine in your own frontier. That is, a stolen magic relic must go to your magic relic shrine.
Relic is really starting to look mispelled here.
A relic of any kind cannot be banked or sold. It can be traded (handed off to another player in a relay), and it can be dropped. It will automatically drop to the ground if you die or lose connection while holding it. If a relic is away from a shrine for more than two real life hours, it will magically teleport back to the place it was last kept, be it the keep of friend or foe. A dropped relic can be picked up by anyone.
Relic keeps cannot be taken over in the sense that the border keeps can be, although all their NPCs can be killed in a raid.
That's the system at this time - in the future, we are planning to integrate the amount of territory controlled with the relic keep's defenses, but that's awhile in the future. We are also discussing a way that the carrier of the relic can be detected, possibly through the use of a "detect relic" sort of spell. No firm plans.