Times Died: 1
Frustration -o- Meter: 4.5/10
Oh.... my..... God!!! This bosses' design almost alone puts him in the top half of the rankings and instantly makes him one of the most memorable bosses of the entire series. What is that thing? Is it a mouth? Is it..... something else?
The fight itself, while not a bad one, is a little more pedestrian. I suppose if you keep things in front of you it become more interesting, but I mostly ran away in an attempt to bait his stomach slam which has a hefty recovery time from which you can do plenty of damage. In fact, I would recommend going two-handed because this battle is mostly about positioning and dodging than having to block. Other than that, there's not too much to worry about except for making sure you kill the Channeler on the ledge above.
Times Died: 1
Frustration -o- Meter: 6.5/10
I have a confession to make: I couldn't kill Priscilla on my first play-through. She's the only boss in the game who asks you to leave and say she doesn't want to fight you. She sounded so sincere (although she was definitely wrong about this world's inhabitants being "peaceful"), I just didn't have the heart to fight her.
Priscilla makes for a cool boss in a lot of different ways. First off, she lives in a painting! The Painted World of Ariamis is beautiful and as far as I'm aware is unique in setting and style in Dark Souls. You get a great run-up to her with the undead dragon, and the coliseum-like building is a neat idea for a boss fight. The mechanic of her turning invisible with the footprints in the snow is well done, and overall this fight just feels right. Even more interesting is her lore; what is her doll doing at the Aslyum? Was she an experiment of Seath's? Why was she sealed away? To this day, Priscilla remains one of the most interesting and enigmatic bosses in the game.
Times Died: 2
Frustration -o- Meter: 8/10
An imposing figure with an army of skeletons to back him up, Gravelord Nito's domain will have the player on edge even before he goes through the fog wall; behind Sen's Fortress Tomb of the Giants is perhaps the most unwelcoming and frustrating area of the game. While patience is the order of the day for this boss, his run-up and appearance are likely to induce anything else but that, and in many ways that is Nito's greatest asset.
With an unblockable ranged attack it is best to stick close to Nito who is relatively slow although this method has its own danger of attracting his skeleton posse. With so many enemies it can be easy to get cornered if you fail to keep strafing so be sure to take advantage of Nito's AoE to break up enemy attacks. I would suggest using a divine weapon and a high stability shield, and I would highly recommend kindling your bonfire because you're going to need those Estus Flasks; Nito is that challenging. Keep a cool head and keep on the move though, and I promise you'll be back in the warm sunlight of the Firelink Shrine before you know it.
Times Died: 3
Frustration -o- Meter: 7.5/10
Queelag is a fast and hard-hitting boss at the end of the particularly imposing and nerve-racking level that is Blighttown. For low endurance or health players her fire sword and lava attacks can be devastating but with practice can be avoided or even exploited. If you flank her too badly, however, she will use a hefty magic attack that is likely to drain most of your HP. In this respect, Queelag comes across as a faster, more unpredictable boss than what the player has seen up to this point and has no easy to spot weaknesses. Add this to the fact that the player has to pass through a poisonous swamp just to reach her, and Queelag can become one of the most disheartening bosses you'll see early in the game.
For those inexperienced or struggling, I would recommend killing and summoning Maneater Mildred (for which you need to be human, of course), who does fairly well at tanking allowing the player to snipe or use magic safely from afar. Most of the time, this will provide you with an easy win, but even then make sure to keep on your toes as Queelag is particularly mobile and can fly across the boss room, despite it size, at a moments notice.
Times Died: 2
Frustration -o- Meter: 6/10
In my opinion, Seath is one of the best bosses in the game. First of all, his run-up is awesome. The Duke's Archives is one of the most visually engaging levels in the game, and the scripted battle with Seath and then your imprisonment is one of the more interesting plot points of the game. After the Archives is the Crystal Cave, a beautiful and wondrous land filled with invisible pathways crossed by leaps of faith Indiana Jones style. Then, the player must dart past Seath himself and destroy the Primordial Crystal that gives him limited immortality; only when all this is done can the true battle begin...
Seath's boss fight is surrounded by lore that can be seen everywhere from the enemies you face, to the environment, to the battle itself. The player hears much about Seath well before he fights him, and this build-up adds tension to the fight. This battle just feels massive, that there are stakes to be won or lost. Overall, the Seath fight is dripping with drama and story that can be felt from all directions in a way that is nearly unprecendeted, even for Souls games.