There is currently a Glitch in Primordius Chamber which enables you to enter Ra-Den Chamber In Normal mode or Heroic mode before You actually kill Lei-Shen, On normal mode he isnt spawned and there is only his room with no mobs whatsoever so only good if you are curious on how the room itself looks like, i am not sure if he is spawned on Heroic mode before you kill Lei Shen HC as i have not tried it, if it is however you can move the topic to Exploit Section since that would be Overpowered as hell since he does drops some Best in Slot items and if your lucky you can cheat your way towards Realm first Ra-Den kill, but as i said i am not sure about this as i have not tried it on HC, So here is what you do.
1. You Need to have a warlock in your raid Grp
2. Click, where you see the Purple Circle on the image you tell warlock to put up a summoning portal
3. once portal is up Let people summon you while they are standing inside the inner circle of the primordius chamber
4. You are now glithed under the floor and you are able to get to Ra-Den Chamber
5. ?Profit?