Dark Souls 3 Walkthrough: Irithyll of the Boreal Valley, Pontiff Sulyvahn Boss Fight, Water Reserve
Once you defeat the Old Demon King in Smoldering Lake and explore the area it's time to get towards the real Dark Souls 3 area where the Boss, Area Mechanics, and enemies are the toughest in the game. Here you will have to face some new kind of Enemies which includes Burning Stake Witch, Irithyll Soldier Slave, Sewer Centipede and much more. So let's start with the walkthrough.
Irithyll of the Boreal Valley Bonfire
Heading Upstairs after Taking down Old Demon King will get you to this New Area called Irithyll of the Boreal Valley. First Lit the Bonfire on the left and then head down and as you enter the Bridge a Sulyvahn's Beast will appear right behind, kill him to get Pontiff's Right Eye who is the Main Boss of the Area.
Central Irithyll Bonfire
Get across the Bridge to Lit this Bonfire and from here you will have two options to continue. One will be the side quest from one of the NPC(only if you haven't joined any covenant) and other will be the main quest. Head up and get ready to face some new enemies who are quick but have fairly less health. Head up and take some Irithyll Slaves then on your right will be Burning Stake Witch along with some more Irithyllian Slaves. Try to separate them and take them down which will make it real easy.
Church of Yorshka Bonfire
As you move ahead you will find two of the Pontiff Knights patrolling the area so be extra careful and try to take them one by one. Take a right and then the enter the Church on the left to Lit up this Bonfire. Now head back to the area where you found the Crystal Lizard as there is a Shortcut to avoid a bunch of Elite enemies.
Once you reach the area hit the first railing to open the Hidden Stairs down and one of the Pontiff Knight is waiting for us. Head Down and you will meet Cathedral Evangelist again so try backstabbing her to drain her half of the health. Loot the area then opens the Door which will bring you back to the Central Irithyll Bonfire, rest there and fast travel to the Church to continue the Main Quest.
Take Left and keep moving until you come across the Boss Gate, but first, we need to clear the area with Pontiff Knights and Burning Stake Witch. Take them down and near the stairs is the Illusory wall on the right where you get the Lighting Gem, so hit and access it to grab the items.
Distant Manor Bonfire
Head outside and grab the Items then head down the path where you find too many Witches Slaves and some Avaricious Being. Kill a few of them and head straight out then head the staircase on the right. The First wall is the illusionary wall so do grab the Crystal Lizard while the rest is filled with witches. On you, Right is an open railing so you can jump down and kill another Avaricious Being and head straight grab all the loot. Enter the Castle from the Left and there is a Bonfire in there so Lit it up to save your Progress.
Once you're done saving your progress head outside and now we can enter the Green path(sewers) which was on the left before we entered the Castle. Get inside and you will encounter few of Sewer Centipede. Climb upstairs from the left and enter the Castle again now keep moving straight and then Left where you will see Pontiff Knight, but make sure you get passed him as there are Enemies with the great bow upstairs which may kill you.
Let him chase you and kill him outside then get inside and climb the stairs from the left and take another Knight and finally get your hands on the 3 Treasure Chest. Head out and climb up on the left and you will have another Dark Spirit Invaded so take him down and continue up where you see the enemies are coming until you reach to take the lift up from the left and open the Cage and get back to Church of Yorshka to save your progress.
Now that you have grabbed all the loot and explored the area it's time to take the area, Boss. Head out and take the same Elevator down where you came from then climb up and before going inside the Castle take a shortcut and drop down from the Left to avoid a whole lot of invisible Witches. Climb the ladder and kill few of the enemies then down and out from the right. Before we meet the Boss there are two of his Best Knights Guarding so take them down and then Enter the Area.
Pontiff Sulyvahn Boss Fighter
This Boss is vulnerable to Parry so make sure you are good at it and we have a separate guide for Pontiff Sulyvahn Boss Fight where you explained about this weakness and strengths so make sure you visit this Guide. Once you are done killing the Boss, Lit the Bonfire and thus completing the Walkthrough. One part of the Dungeon is still left where you need to head out and then climb on the Left Stairs.
Water Reserve Bonfire
You can skip all the Giants and head inside the Castle, hit the Wall on the Left to Open the Illusionary Wall and head inside the Water Reserve, but here you will face two of the most dangerous Sulyvahn's Beasts and killing them will get you Ring of Favor and a Bonfire - Water Reserve. We will continue with the next Walkthrough - Irithyll Dungeon, or else you can check out our Dark Souls 3 Wiki page to know more about the game, collectables and weapon Locations.