Because Realm of Pain is now a quest destination, I have made a few modifications to it.
1. It is harder to get into the temple, you need to place certain items within the ritual circle outside the temple barrier. This will lower the barrier for 10 minutes, unless the Dark Lord Baaleos (me) decides to raise it again... (Evil Laugh)
2. When visiting the temple while doing the Dark Faerie quest line, you will get Mob Spawns - they look like Void Wraiths, but might be stronger, or weaker... not sure yet. (still need testing)