Yahar'gul, Unseen Village
After defeating the Blood-starved Beast you can enter the Healing Church Workshop, but you'll eventually run into a locked door. The key to that door can be found after you defeat Rom, the Vacuous Spider in Byrgenwerth and gain access to Yahar'gul, Unseen Village. Once you've explored the Unseen Village and gained access to the Yahar'gul Chapel lamp, you can find the key required to unlock the door in the Healing Church Workshop and enter the Upper Cathedral Ward area.
From the Yahar'gul Chapel lamp, turn around and head up the stairs. Remember that you'll deal with a laser and some Old Hags. When you reach the top of the stairs, search the far left side of the area (just before the next set of stairs to the left) to find a hole in the railing. Drop down to the area below and head through the doorway to the right.
In the next room there's a Brute to the right, but first take down the Bell Caller around the corner to the left. Drop into the lower area in the middle of the room through the hole in the stone railing near the entrance to the room. Search the corpse below to find the Upper Cathedral Key. Now you're ready to return to the Cathedral Ward lamp and make your way into the Upper Cathedral Ward.
When you're ready, head to the Cathedral Ward lamp. Go into the next room, then through the small opening to the right and up the stairs. Move into the lift and stand on the weighted plate to move up. Be careful as you move into the next room because there's a Wheelchair Blunder waiting there.
Unlike the first Wheelchair Blunder who only had a basic gun, this one has a mini-gun that he won't hesitate to use. If he doesn't start shooting as you approach the opening into the room, walk slowly out into the room then duck back into the hallway to bait him to shoot. Once his first round is done, quickly run over to kill him. He has very little health and goes down easily once you get close. Open the chest at the end of the room to find a Communion rune (increase Blood Vial limit).
Head up the stairs to the side of the room to see a bridge. Several Henchmen (two with guns) are in the room directly across the bridge. When they see you they will run out to attack or start shooting. If you have problems reaching the room to kill them, you can move out slightly to get their attention and one or two will chase you back into the room where you can kill them in smaller numbers, then quickly run across the bridge to avoid the gunfire.
Kill any remaining Henchmen in the room and open the chest on the far left side to find a Bloodtinge Gemstone. You have now entered the Healing Church Workshop.
Healing Church Workshop
Head back inside and up the stairs to find a Henchman and a Wheelchair Blunder waiting at the top. Take out the Wheelchair first, then the Henchman. Just outside is a Brick Brute with slightly more health than the ones from the previous areas. You can still fight it the same way, but it will take a bit more than a single shot and critical strike to finish it off.
Go outside and look to the left to see another Wheelchair Blunder and a Henchman with a rifle. Kill them both, then search the body next to them to find a Thick Coldblood. Continue to the left and up the ladder ahead.
When you reach the top there's a note on the ground to the right, but not much else. Head left and pass the entrance to the next room for now. At the end of the path is a corpse that holds a Thick Coldblood. Collect the item, then head back to the entrance you just passed.
Two Wheelchair Blunders with Flamesprayers (flamethrowers) and a Henchman wait inside. Take them out and then open the chest to the right of the next doorway. Inside the chest is a Radiant Sword Hunter Badge (key item). Continue through the doorway and into the room with a lot of vases. There's nothing in the vases, but feel free to break all of them if you'd like. With the Upper Cathedral Key you can now open the door on the other side to enter the Upper Cathedral Ward.
Upper Cathedral Ward
Head up the stairs and kill the Squid Lizard enemy straight ahead. These act similar to Imps except they don't drop the nice loot you receive from the former. Head up the stairs to the left and then circle around to the gate to find a corpse that holds a Blue Elixir.
Continue across the bridge to engage the two Gravekeepers and three Squid Lizards on the far side. Activate the Upper Cathedral Ward lamp at the end of the bridge, then make your way up the stairs ahead. There are two Squids near the top of the stairs and another group to the right. After killing the Squids to the right, search the corpse here to find a Great Lake rune.
Turn around and head to the other side of this path to find more Squid Lizards. Continue down the path and head to the left of the stairs to find a few Crazed Crows. Take them down then search the corpse here to obtain a Frenzied Coldblood.
Head up the stairs you just passed, then continue up a second flight of stairs to face another Gravekeeper at the top. A Leech Warlock waits in the next room, so be very careful of its magic and do not let it grab you. Search the nearby corpse to obtain the Choir Garb (chest attire), Choir Gloves (arm attire) and Choir Trousers (leg attire).
Go through the doorway and down the hallway to the right to find a corpse at the end that holds a Madman's Knowledge. When you turn around to head in the opposite direction a Nether Beast crashes through the wall behind the corpse. Dodge back to avoid the initiate attack, then finish off the Nether Beast and go through the doorway to the left at the end of the hall. Kill the Leech Warlock in the next room, then open the larger door to the right. Examine the statue ahead to obtain the Make Contact gesture
Head back to the hallway and make your way to the other side of the hall. Open the door on the right and head down the stairs in the next room to see the light in the ceiling fall and four Nether Beasts appear. Use your Torch or Hand Lantern to light the area as you battle these two enemies. On the far side of the room is a large door. Search the corpse directly in front of the door to find a Ritual Blood Chalice Dungeon item.
Turn around and search the area to the right of the stairs to find a doorway that leads to a hallway. Go down the hallway and quickly kill the Imp at the end, but watch out for the Leech Warlock in the next room. Continue up the ladder in the room and through the doorway to the right (not the doorway in the corner) to find another Leech Warlock. Search the corpses in the hallway to obtain another Blue Elixir, Blindfold Cap, two Madman's Knowledge and two Pearl Slugs. Open the door on the left at the end of the hallway so it's no longer locked from the hallway.
Head back to the room at the top of the ladder and continue through the doorway in the corner to find two more Leech Warlocks. The second Leech Warlock drops the Orphanage Key, which you'll need soon. Open the door on the far side so it's no longer locked, then head back into the main room and through the doorway on the right to find another hallway. Kill the Leech Warlock and search the corpse to find a Cosmic Eye Watcher Badge (key item).
Go back down to the door where you found the Ritual Blood item. With the Orphanage Key in-hand the door will now open. Search the corpse in the middle of the next room to find a Frenzied Coldblood, then pull the lever to the right to open the gate and create a shortcut back to the beginning of the area.
Turn around and head up the stairs to the right, then up the second flight of the stairs. Kill the Cranium Creature at the top and walk into the large room ahead. When you reach the lower portion of the room the boss battle against the Celestial Emissary begins.
Boss Fight with the Celestial Emissary
- Beat the Celestial Emissary to receive a Communion rune.
The trick to this boss battle is similar to the mechanic behind the battle against Rom. There are a bunch of Cranium Creatures in this area. You need to continue attacking them until you see the health bar for the Celestial Emissary start to go down. This indicates that you've found the boss.
Attack the Celestial Emissary until it grows into a giant version of the Cranium Creatures, then quickly move up the stairs to the balcony area, all the way to the end, then drop back down into the lower area. The Celestial Emissary moves considerably slower than the Cranium Creatures, but the Cranium Creatures will not drop down to follow you. Instead, they go all the way back around and take the stairs down. Use this time to attack the Celestial Emissary without having to worry about the ancillary enemies.
Depending on your level when you fight this boss, you may not have to worry about this tactic. To avoid most of the Celestial Emissary's attacks, stay behind it as you use your own series of attacks. If things get too crowded again, head back up the stairs to move the Cranium Creatures away, then drop down and engage the Celestial Emissary again. It won't be long before the Celestial Emissary goes down, giving you the Communion rune as a reward!
After defeating the Celestial Emissary, head to the top of the area and look for a large glass window. Attack the window to break it, then head into the next room and kill the Squid Lizard directly ahead. Make your way around to the far right to find a corpse that holds the spell, A Call Beyond, kill the two Cranium Creatures through the opening at the end, then head down the lift. Kill the three Squid Lizards at the bottom, then head into the Altar of Despair to engage the Ebrietas boss.