Chaos Witch Quelaag
Half spider, half sexy lady, Chaos Witch Quelaag will quickly end you if you stare for too long at those sick nasty spider legs. Actually, the fight is fairly simple. Don't stand in fire. Roll dodge her sword attacks. The biggest thing you'll want to watch out for is her brutal AoE ability. When the human portion of her body bows down, that's your signal to get the f*ck out of there.
Excuse us for the first minute of this boss video. We ran around a circle in panic because we never fought an invisible boss before. Watch for Priscilla's footprints in the snow—that will give away her location. Be sure to keep that shield up in case you lose track of her. Get a few attacks in, then roll away. This fight is for babies.
The Demon Firesage bears a striking resemblance to the Asylum Demon from the tutorial area, but he has a few more attacks. The two most annoying abilities in his arsenal are some fire spells. When he plants his spear in the ground, run. This signifies that he's about to use a rather powerful AoE explosion. He does another fire attack that does damage in a frontal cone. Dodging this attack is rather difficult. When he does a leaping axe attack, roll toward his body and get some hits in. Occasionally he'll fly up into the air and body slam the ground. Use this opportunity to score some free attacks.
Dragon Slayer Ornstein and Executioner Smough
This is the first boss encounter where Dark Souls proudly presents its giant middle finger. Two bosses at once, both of which are powerful. Yay! Dragon Slayer Ornstein is agile and does both lightning and physical damage. Executioner Smough, on the other hand, is a bit slower and hits super hard. There's no real easy way to approach this fight. You have to decide which boss to kill first—as soon as one dies, the other gets even stronger. Killing Ornstein first adds lightning damage to all of Smough's attacks. Killing Smough first means Ornstein grows bigger in size and strength. Either way, expect to get your skull caved in a time or two. Take advantage of the pillars to line of sight attacks. Chip away when the opportunity arises, but expect a lengthy fight.
If you’ve got some humanity to spare, you can summon Solaire of Astora to come help you if you’re alive. His summon symbol is at the top of the short staircase beside the entrance to the boss area. He makes this fight much much easier as he will essentially tank one of the bosses, allowing you to focus on the other. If you prefer real players to AI bots, this is a great fight to try summoning some help from other players.
Another Lord Demon encounter, the Four Kings are intimidating at first. You must have the Covenant of Artorias ring equipped to access the Abyss, which is where these bosses are housed. At the beginning of the fight, only one of the kings will be active. Eventually, all four will be out at once, and they share a health pool. We recommend equipping your most defensive armor (probably the Havel's set from Anor Londo), as the Four Kings don't hit terribly hard.
Their magic abilities are what hurt the most, and they typically only cast them if you're at a distance. Get up close, attack a king until it dies, then move onto the next. They will respawn shortly after being killed, but managing one or two at a time is far easier than all four. Occasionally, the one you're attacking will charge up a spell, emanating a purple aura in the process. Quickly get your shield out, as this magic AoE ability will do far less damage when you're blocking. Keep your health up as often as you can, too—they will sometimes use a grab attack that can easily drain half your health.