Smelter Demon

The Smelter Demon is an optional boss in Dark Souls II. Created from a mound of iron by the Old Iron King, it betrayed its master, leading to his death and downfall of his kingdom.

Biography
When the Iron King's Iron Keep slowly fell ruin due to the mass amount of iron weighing down the castle, he thought of the plan to use his iron, alongside the exposed fire that came from the lava underneath his castle, he could create life. Using his Scorching Iron Sceptre, he molded metallic automatons and granted them life with a soul as their core.

When the Smelter Demon was formed, the king ordered his pyromancer follower, Magus Eygil, to use fire to ignite the soul that controlled the golem. With Eygil's power, the earth sprouted fire and a beast arose from the flames. But the golem had a mind of its own, and quickly killed the king with one swing. With the Iron King gone, the kingdom fell into ruin.

The Smelter Demon can be found in the ruins of the Iron Keep, beyond the drawbridge with the Alonne Knights. While optional, it is genially required if the player does not want to risk reaching the other side from a shortcut with only one shortcut. The Smelter Demon attacks by swinging its sword. While it moves rather slowly, all of its attacks can deal critical damage if the player is not on their guard. Once it loses a fourth of health, the Smelter Demon buffs himself, causing the flame in its chest to burn hotter, creating a flame aura around his body that hurts the player when they are very close. Once it loses half of its health, it embeds its sword with the flames. Once the golem goes down, the rest of the Iron Keep is opened for the player to visit.

In the Crown of the Old Iron King DLC, a second Smelter Demon can be fought, again completely optional. It is unclear if this is the same Smelter Demon, as its horns bend upwards instead of sideways, and it has a blue core instead of red. It fights identically to the first Smelter Demon, but it has more health than the first, and its attacks deal magic damage rather than fire. It also appears to be more aggressive than the one in Iron Keep given how much faster it is. Defeating it makes it drops another Smelter Demon soul.

Trivia

 * The Smelter Demon's boss theme is shared with the Ruin Sentinels.
 * The Pursuer appears in the Smelter Demon's arena after its defeat.
 * The Smelter Demon soul can be given to Weaponsmith Ornifex in exchange for the Smelter Sword or Aged Smelter Sword. The blue Smelter Demon must be fought first to unlock the Aged Smelter Sword.