Titanite demon down in one go. I had only 1 potion left too, so it was relatively close. I'll proceed onwards after a short break.
Edit
How do I summon the extra guy?
Edit2
Yea, no master key. I took witches amulet.
Kudos to you! I always went with the pendant ... it's supposed to reveal more story, but I never got it to work. Ended up trading it to Snugly for a Souvenir of Reprisal because farming the harpies in the painted world svckS. (You need 10 of them to earn a secret miracle, from a secret coven) Anyway, you'll be able to speak with the leader of the Chaos coven.... assuming you can find her

I never bothered with the demon before killing Quelaag, so I always had an incredibly easy time with him. But as the other posters have mentioned, the really tough ones are in areas where you can be insta-killed with a pit-fall. I never was... but it's so damn heart wrenching... Getting pushed RIGHT up to the edge always made me grip the controller EXTRA hard and take a DEEP breath.
Screw the forest and head on down to blight town! However, if you decide to keep on playing and kill the butterfly, be sure you summon Beatrice. IF you summon her, and win, she will be available later on for a MUCH MUCH more difficult fight, later on.
*is very excited for you to get to Sen's Fortress, and Anor Londo. I can't wait to hear what you think of Smoug-en-Stein.
Also, be sure to talk to "Sir Onion" (Siegmeyer) before you open the way to Sen's Fortress. If you don't he will vanish, and you'll miss out on one of the super-rare items.