Seath the Scaleless

Seath the Scaleless is a boss in Dark Souls.

Location
Encountered in the The Duke's Archives and the Crystal Cave.

Plot
The Chosen Undead must confront Seath in order to retrieve his Bequeathed Lord Soul Shard, necessary to satiate the Lordvessel.

Lore
The albino dragon, Seath the Scaleless, betrayed his own by aiding Gwyn, Lord of Sunlight, during the war with the Everlasting Dragons. He acquired the Primordial Crystal; a sacred treasure pillaged when he turned on the ancient dragons, granting him immortality and making him a "true Undead." Gwyn entrusted Seath with Dukedom for his role during the war and gave him a fragment of a Lord Soul.

During his time as Duke, Seath became obsessed with his experiments and research, amassing countless tomes and eventually driven mad. The Channelers, sorcerers under Seath's command, traveled to far lands in order to acquire more specimens. Amongst those captured were maidens. Many "mistakes" resulted in the process of Seath's experiments.

The six eyes of the Channelers compensated for Seath's lack of sight. Crystal Soldiers populate the fortress, as well as a few Serpent Soldiers to help guard the prison.

Seath is said to be the grandfather of Sorcery and is the object of the infamous sorcerer, Logan's, obsession. Seath's creations include the Pisaca, Moonlight Butterfly, and Crystal Ember.

Strategies
Staying at his side makes it easier to stay out of the area-of-effect of his breath attacks, and he won't be able to hit with his claws or tail as easily.

It is also possible to use only a bow against Seath with great success. Get a good distance away from him and it is possible to get 4-5 shots in before he gets too close. The only real danger in this strategy is when running past Seath to gain some distance.

His only long range specific attack is the far curse beam. That means if players stay at a distance, one can lure him to fire the beam and charge his defenseless body.

Crystal curse explosion triggers when the player cannot be reached by any of Seath's other attacks; usually when situated behind Seath with the tails just out of reach. One strategy is to begin sprinting a good distance away from him once he arches forward to charge a ball of magic. A second approach would be to develop a high enough curse resistance and block some of the erupting crystals. Immediately heal the damage received before he executes his tail swipes/slams.

A good strategy for acquiring the Moonlight Greatsword is when Seath himself breaks the Primordial Crystal. Wait behind the crystal until Seath starts to rear up his head for any of the Curse Beam attacks. Just before he fires it, start sprinting left or right around the sides and towards his tail. Seath will break the crystal and stun himself, giving the player ample opportunity to attack his tail three to four times. Make sure Seath's tail isn't clipping in the wall before trying.

Also keep in mind that Seath has almost three times the resistance to Magic as he has to, say Fire or Lightning. Therefore Sorcery, Enchanted, and Magic weapons do less damage. A maximized Pyromancy Flame with either Combustion or Great Combustion will burn off the tail in one to three hits, as well as giving the player better control of where to hit the tail.

Close Curse Beam
The first of Seath's Curse Beams: Seath will fire a beam from his mouth in a circular arc close to his body, and crystals will erupt from the ground around where the beam touched.

Breath Crystal
The crystals that erupts form the ground after each Curse Beam attack, they are unblockable and deal continuous damage, as well as curse build up.

Crystal Curse Explosion
Seath's most dangerous attack: Seath will begin charging briefly, and will then erupt crystal from his body in all directions. This crystal eruption is even more damaging than the others, and of course much harder to evade. The only way to avoid it is to get quite far away from Seath's body, out of range of the eruption.

Tail Thrash
Seath will use this if the player stay near one of his three tails for too long. He will begin slamming all three tails down continuously, smashing into you if you are too close. This can even hit multiple times, stunlocking the player. This attack is unblockable

Far Cursebeam
The same effect as the Close Curse Beam, except this is fired in a circular arc further away from Seath's body.

Straight Cursebeam
The last of the different Curse Beam types, Seath fires this in a straight line from the base of his body to the end of the room, in the direction the player is standing.

Left or Right Handbeat
Seath will throw a scooping punch with either his left or right hand. This is incredibly damaging and unblockable, but fairly easy to dodge since his hand hitbox is small.

Trivia

 * In the first encounter, if the player goes back through the Fog Door and is then killed by Seath, they will not respawn at the prison bonfire, instead they will return to the last bonfire they rested at.
 * If the player cuts off Seath's tail, it may not disappear, and will persist after Seath has been killed.
 * Despite being blind, the Hush spell and Slumbering Dragoncrest Ring do not allow the player to avoid detection by Seath.
 * Seath shares his name with a character seen in the King's Field series, however, the Seath in King's Field 2 bears a more humanoid form.