Dark Souls' Artorias Of The Abyss content, which was previously only available to PC players, has now deployed on Xbox Live and PSN. £9.99/1200 MSP will net you new bosses, weapons, armour sets, monsters and levels, which all fit into the existing storyline.
According to the EU PlayStation Blog, the new DLC "lets you unveil some mysteries about the lost kingdom of Oolacile and the (in)glorious past of Artorias, one of the four champions of Gwyn, the lord of Cinder."
It's also a little on the difficult side. Who knew?