In case you were a bit confused from the comments, to sum it up: 1. Go down to the Abyss via New Londo Ruins. 2. There are three new areas that will be unlocked after you complete the Abyss. 3. The Abyss requires a certain ring to be equipped.
I did some serious souls farming, leveled up a lot, upgraded to the end my Pyromancy Flame, killed the Four Knights, but ate dust in Duke's Archives. Huge frustration. At the end fortunately I escaped the damn place.
Unless you are a formidable player, by all means you need magic in order to survive. If I were you, from now on I would do some crazy soul farming and improve the attunement stats so that you can equip at least three magic spells. Pyromancy for powerful close combat hits, or Sorceries for weaker but ranged attacks, it's your choice.