To Link The First Flame
This is probably the ending you’ll get on your first blind playthrough. To link the first flame in Dark Souls III, simply play through the game as per normal until you reach the final boss, the Soul of Cinder. After defeating the boss, look for the bonfire sitting near the edge of the boss arena.
Simply interact with the bonfire, and accept the prompt. This will trigger the cutscene for the first ending.
The End of Fire
To get this ending, you have to access the Untended Graves optional area. After defeating Champion Gundyr, head to dark Firelink Shrine and look for the Eyes of a Firekeeper key item. You’ll find it behind an illusory wall at the end of the corridor on the bottom floor. Roll through the wall, pick up the Eyes, and head back to Firelink Shrine to give them to the Firekeeper. This will cause the background music in Firelink Shrine to change.
After defeating the Soul of Cinder, do not interact with the bonfire. Instead, look to the left of the bonfire and you should find a summon sign for the Firekeeper herself. Summon her, and the ending cutscene will be triggered.
There is also an alternative version of this ending. After the cutscene, as the screen starts fading to black, you’ll have a few seconds to attack the Firekeeper and kill her. If you do this, you’ll get a slightly different version of the End of Fire ending.
Usurpation of Fire
This is probably the toughest ending to get in Dark Souls III, as you’ll have to manage multiple NPC questlines. When you first reach the Undead Settlement, find Yoel of Londor kneeling on the edge of the broken bridge. Talk to him and allow him to join you at Firelink Shrine. Once he’s warped back, go back to the Shrine and talk to him so he can draw out your true power. He essentially allows you to gain one free level. You can gain a free level for every two times you die, and you have to gain five levels from him in order to continue on your path to getting this ending. You have a very short window to get the five levels, so I advise just throwing yourself off the cliff outside Firelink Shrine until you get them.
After leveling up five times, Yoel will be dead the next time you return to his location. Yuria of Londor will appear next to his body. Exhaust her dialogue, and then continue on to the Road of Sacrifices where you’ll meet Anri and Horace for the first time. Exhaust their dialogue, and continue with the story until you reach the Catacombs of Carthus.
When you first reach the Catacombs, take the stairs down right before heading down the main stairs where you get attacked by the large skeleton ball. You’ll find Anri there, lost and looking for Horace. Don’t tell her where Horace is, and continue on your way. On your way to High Lord Wolnir, instead of taking the rope bridge across, head up the path on the right side to find Anri again. Once again, don’t tell her where Horace is. Cut down the rope bridge and head down to Smouldering Lake. From there, hug the right wall until you come to a cave. You’ll find Horace there. Kill him. Head back to Firelink Shrine and talk to Yuria.
You’ll see Anri again next to the church bonfire in Irithyll. Exhaust her dialogue, and then leave. Do not attack the statues at the side of the room. Once you’ve defeated Pontiff Sulyvahn, head back to Firelink Shrine and talk to Yuria. She’ll tell you that preparations for the marriage are ready. Head back to Irithyll and continue onward after the Pontiff bonfire. Before pulling the lever that takes you to Anor Londo, turn around and look for an illusory wall that takes you to Darkmoon Tomb. Talk to the pilgrim to get a ceremonial sword, and then head into the tomb and interact with Anri to initiate the marriage.
From here, just play the game as per normal, but do not reverse your hollowing or this will make Yuria angry. Once you defeat the Soul of Cinder, interact with the bonfire, and you’ll unlock the Usurpation ending.
Be sure to check out our Dark Souls III wiki for more tips and tricks.