The Darkeater Midir boss follows on from the Ringed Inner Wall area of the Ringed City DLC, acting as the secret boss you may have heard about. It's an optional place to branch off from the main sequence of the story, but what would Dark Souls be if you didn't stray off the beaten track for a surprise beat down?
We'll be covering that here, but if you need help with other parts of the DLC meanwhile, then take a look at our Dark Souls 3: Ringed City guide and walkthrough hub for plenty more.
Dark Souls 3: Darkeater Midir - how to find the secret boss
If you've been following this guide, you would have already spoken to the NPC behind the door from the Ringed Inner Wall bonfire, at the top of the stairs just before the swamp. You would have also beaten the dragon on the bridge, knocking it into the abyss below. Well, now it's time to go after it.
Now get to the Ringed Inner Wall bonfire again and take the elevator down, jumping off halfway down, through the opening where you went for the ring earlier. In a room up there, you'll find a bunch of knight statues. One of them has no sword - striking it will reveal an illusory wall. Now drop down into the void and get ready for a tough fight.
This deadly dragon is much more of a threat down here in its lair. When the fight starts, it will either breathe fire or charge at you. In either situation, the best thing to do is roll left or right and keep on rolling. If it does charge at you, get ready to roll again when it stops, as a tail whip usually follows and that will end you in one strike.
The safest place to be is at the side of its head where you can hack away. When it breathes fire, run to the back of its tail and get in a few cheeky strikes from there where you should be safe from the blaze. Again, watch for the tail whip after a couple of hits.
When it takes flight, it's very hard to avoid the fire it breathes from there, so be sure to top your health up if it heads into the air, then try get directly under it if you can. If you have a shield, keep it up and you should negate some damage. Fire-resistant gear is also a good shout. If you stay close, it often stops it using this technique, however.
Once down to around half health, its attacks will become more frenzied and it will chain more moves together. Try to keep calm and just treat it like the first stage of the fight. The same tactics apply, but you will need to do a bit more rolling.
When it has about a third health left, it will start doing an area-of-effect attack. When you see black energy gravitating towards it, roll away. It might fire out humanity-like projectiles, too, though these are easily avoided. Use the exact same windows to attack as you did in the first phase and you should have hacked through it in no time.
If you've been targeting the head, there's a good chance you will stagger it. If you see it drop approach the head again and tap a light attack for a critical hit. The Spears of the Church and a new boss soul are yours.
That should be everything here - heading back to the main sequence though, you can progress on to the next area after the Ringed Inner Wall, which is covered in our page on the Ringed City Streets, Dragon, and the Moaning Knight; or, head back to our hub page for the Ringed City DLC walkthrough and guide, and choose your next steps from there!