One of the toughest areas in the game - but you'll be fine.
Dark Souls 3: Irithyll Dungeon to Archdragon Peak
Although it's hidden in an optional area, itself only accessible after beating an optional area, Archdragon Peak is the real endgame area. The ultimate boss here is probably the toughest you'll face, and the baddies in Lothric Castle are nothing on the aggressive denizens of the temple. On the other hand, you need to do this if you want to become a dragon, so here we go.
You need to have completed Consumed King's Garden, beaten Oceiros, the Consumed King and collected the Path of the Dragon emote from the corridor leading to Untended Graves in order to access Archdragon Peak.
With that done, head to Irithyll Dungeon and make your way to the rocky, cliffside path between the patrolling Jailers and a shortcut lift; one easy route is straight into the dungeon, out the shortcut window, down a hole from the room above the giant’s pit, across the bridge and down the rat tunnel.
You'll know you're at the right spot when you see multiple seated corpses, including a very draconic figure. Stand in the empty place between a couple of the figures and use the Path of the Dragon Gesture. You won’t have to wait very long until your body slumps and you are transported to Archdragon’s Peak.
What a lovely place! Is it real at all? Who cares! There’s great loot, and great fights. If you are in Ember form prepare for punishment; this area is a favourite for late game invasions.
Bear left as you move forward and collect a Soul of a Weary Warrior. Further up the track, two dragon hybrids are patrolling; one goes left and one goes right, so be sure to get them both. At the fork in the trail where they meet, climb the steep slope to grab a Lightning Gem, then come down again.
Both paths lead to the same place, but there’s a dragon hybrid sniping with fireballs overlooking them. Take the right (lower) path and you can dash over to shelter behind some rocks near a lift we’ll activate later. You can snipe back here. There’s a second sniping dragon hybrid who’ll aggro if you stroll over to the end of the left (higher) path to grab the Homeward Bones there; advance a little further towards him to hide behind some more rocks, all the better to snipe him.
A melee dragon hybrid will attack from the right as you move up the path, and there’s another dragon hybrid to the left of the rock pile. When it’s safe you can collect a Titanite Chunk from the far side of the rock pile.
Continue in this direction, ignoring the rocks on the right, to grab an Ember and activate the Archdragon Peak bonfire.
Head up the stairs and collect the Soul of a Nameless Soldier on the right, then the Titanite Chunk on the left. Continue on past the last item and up the narrow stairs.
See that dragon hybrid with his back to us? Tempting, isn’t it. Don’t be fooled: there’s another dragon hybrid almost invisibly crouched against the rocks along the bridge to him, and as for the one with its back to you… it’s not a normal one. It’s a giant. And unlike most of the enemies we’ve met so far, wow: it’s really not stupid, so you’ll find it very hard to cheese. That said, it will completely ignore you if you stay a safe distance from it, even if you steal over and collect the Titanite Chunk on a corpse beneath its position. Our advice is to aggro it, run to where it was and grab the Ancient Dragon Greatshield, and then leg it for the bonfire. If you are very stealthy – very light armour and Spook – you can grab the shield and sneak away with aggroing it, even.
However you navigate this area, ignore the gate for a moment and head down a small path to the left of it (as you face it). There’s a dragon hybrid patrolling here, and just beyond it, the Lightning Clutch Ring.
Back to the gate. Pull the lever to open it and be ready for a boss fight.