Like everything else in the Dark Souls universe, accessing the new "Artorias of the Abyss" DLC isn't easy. The new content adds a whole new area, complete with new enemies, NPCs, weapons, and armor. When I spoke with a Namco Bandai rep at E3, I asked how players would gain entry into the new area, Oolacile. He was kind enough to oblige.
Simply accessing the new land from a menu screen or via the Lord Vessel (the game's fast travel system) will not do. Like the Painted World of Ariamis, players will be required to bring a particular item to a certain location to play the "Artorias of the Abyss" DLC. I'll let you know what you need to do after the break. Warning, spoilers and whatnot.
You can access Oolacile through the Darkroot Basin. Not so fast! Let's see if I can do this off the top of my head, sans the Googles. First you'll need to get the Broken Pendant from the Duke's Archives. Wait, wait, wait. Before you can access the Duke's Archives you'll need to give the Lord Vessel to Kingseeker Frampt or Darkstalker Kaathe. To get the Lord Vessel you'll need to defeat Dragonslayer Ornstein and Executioner Smough. To get to that diabolical duo you'll have to navigate Sen's fortress. To get to Sen's Fortress you'll need to ring the Bell of Awakening in the Undead Parish and the other Bell of Awakening in Quelaag's domain. To even get near the Bells you'll have to traverse the Undead Burg, the accursed Blighttown, and if you really want to, you can take a stroll through The Depths.
This is the Hydra. It's actually waaaaaay bigger than it looks here.
Before you do any of this you'll need to escape the Undead Asylum. Oh, and if I mentioned an area without mentioning a boss, there's a boss. There's always a boss. In some cases there are two. And if I mentioned a boss without mentioning a perilous, trap-filled, hellcrafted dungeon, castle, or other horrible area, there's one of those, too. And don't forget a simple missed block can get you killed by the lowliest grunt. And then, of course, there are the random invasions by other hostile players, who are far more dangerous than all but the most powerful enemies. So after you do all that, (and I'm sure I missed plenty) you can now access the DLC, as long as you follow these steps:
Kill the Darkroot Basin Hydra. You can't miss it. It's the giant creature that's killing you whenever you try to cross Darkroot Basin. Kill it back. Behind the Hydra will be a small alcove. It's to the left. Trust me, stay to the left. Leave the area and come back or save and quit your game to make a Crystal Golem appear in this alcove. Offer it a flower and befriend it. No, I'm kidding. You kill this too. Dusk will appear. She says some stuff. Answer "yes," or you're screwed until your next playthrough. Go to the Duke's Archives. There will be another Crystal Golem near the first bonfire. He's new, as in, he wasn't here before the DLC. Can you guess what you have to do? That's right. Kill that sucker. He drops the Broken Pendant. Take the Broken Pendant back to the same alcove where you rescued Dusk in the Darkroot Basin. There you will find a black mist. Touch it. Go ahead. You know you want to.
Congratulations, you are now in Oolacile, the land of the "Artorias of the Abyss" DLC! Also, you're most likely seconds away from dying. Enjoy!
For those of you who are curious, it takes about 15 to 25 hours to get to this point in the game. I've got a character partnered with another player and we are just beginning the Duke's Archives with 26 hours of playtime. Keep in mind, we've done everything twice since we're co-oping the game together, so that's closer to 13-14 hours in a single playthrough. It's even less than that if you cut out all of our summoning misadventures. Either way, if you're just starting a new character or a New Game Plus, you have a bit of a trek before you get to the "Artorias of the Abyss" content. Of course, you could always speed run it in about 45 minutes, if you're a ninja.