Kiln of the First Flame

The final ash-covered realm where the Soul of Cinder waits and the ending is chosen.

Bosses

Soul of Cinder: Final boss. It swaps fighting styles in phase one, then mirrors Gwyn in phase two.

Place every Cinders of a Lord on its throne, then use the Firelink Shrine bonfire to travel to the Kiln of the First Flame.
With all four Cinders on their thrones, the Shrine Handmaid stocks a single Titanite Slab.
You arrive at the Flameless Shrine bonfire. Back at Firelink Shrine, the Skull Ring now lies on Ludleth's throne.
With 8 Dark Sigils you can summon Yuria of Londor and the Londor Pale Shade. If Yuria survives, the Darkdrift and Black Set appear at her spot in Firelink.
Defeat the Soul of Cinder for the Soul of the Lords.
Which endings you can choose depends on what you did earlier; see the Endings page.
Ending 1: touch the bonfire to link the fire for To Link the First Flame. Followers of Yuria must have the Dark Sigil cured first.
Ending 2: after giving the Eyes of a Fire Keeper to the Fire Keeper, use her summon sign by the bonfire for The End of Fire.
Ending 3: during that ending's final scene you briefly regain control; attack the Fire Keeper for an alternate ending. No achievement.
Ending 4: with all 8 Dark Sigils from Yoel and Anri, interact with the flame to take it for The Usurpation of Fire.