This fight can be a pain early on. If you don't have access to any spells, we recommend snagging the Longbow from the area between the Darkroot Forest and the Valley of Drakes. Chip away at the creature's health while it's airborne, but pay attention to its magic attacks. It's best to roll dodge its magic when possible, as blocking does little to nullify the damage. At times, the Moonlight Butterfly will land on the ledge. Start slashing away until it charges up a magic spell—when you see it start to glow, get away.
If you’re alive, you can summon an AI companion witch whose long distance spells can be extremely helpful here, especially if you’re a melee character. Her summon symbol is hidden in some grass at the bottom of the tower leading up to the boss’s room.
Pinwheel throws spells at you while creating mirror images of himself. He's not terribly difficult, just rather annoying.
Seath the Scaleless
Reasons why Seath the Scaleless didn't have any dragon friends: He hangs out in a room that can only be reached by traversing a maze of invisible paths; he sprays friggin' crystals from his mouth; those crystals can curse you. The trick to this battle is to get to the rear of Seath's room and destroy his magical crystal thing. Otherwise, he regenerates his health. Once that's down, bait him into using his crystal laser beams, then run up close and hit him in the dragon jewels. Be careful, though, as he does have one crystal AoE that can quickly destroy you. When he bows down and starts groaning, run.
Your first real boss fight! The Taurus Demon is pretty simple. Once he jumps down from his tower, run back toward the light gate you walked through to reach the ramparts. Next to the door is a ladder. Climb up and do a plunging attack on the boss. Lure him away from the ladder, dodge his attacks, then run back up the ladder and repeat. You can also avoid virtually all his attacks by simply rolling between his legs every time he winds up to swing at you.