I recorded this video earlier today:
A video walkthrough of the Obsidian Sanctum, the platforming dungeon beneath the Eternal Battlegrounds. I was very fortunate that the few enemy players I came across did not engage me, although there was a very scary moment (not in this video) where someone sprang the minotaur trap. If you can complete the Obsidian Sanctum, you'll receive an achievement and a very nice reward of Badges of Honor and blueprints. I strongly recommend you bring speed boosts and disable the 'double tap to dodge' option!