Heart of the Abyss

Godly Tier.

Requires "Nightmare of Yggdrasil", "The World's Dawning", "Straight from the Heart", "The Decaying Blossom" and "A Requiem Dance" finished. Also requires 92 Wispweaving, 85 Concreation, 80 Extracting, 87 Digging, 90 Woodcutting, 87 Summoning and 85 Constitution.

1. Start by talking to the Requiem Angel in the place you started "A Requiem Dance", she will inform you that a new evil has sprouted and will need you to dispose of it. She will tell you that she needs you to talk to Valeska's mayor about the situation.
2. Teleport to Valeska and enter the mayor's mansion only to find out from the clerk that the mayor has gone to the Nightleach Graveyards to check on a new threat. You need to ask where the mayor has gone in order for the mayor to show up there. Nightleach Graveyards is north of Valeska so enter there.
3. When you enter the Nightleach Graveyards head straight to the mayor and the mayor will be trying to attack you. You will need to fight off the Infected Mayor Lv 115. He mostly uses melee but he will attempt a magic spell that drains 20% of the damage done on you below 50% hp.
4. After defeating him, the mayor will return to normal and thank you for snapping him out. Go through all the dialogue and the mayor will then instruct you that a new entity is trying to take over. The Elven Seer will then teleport and surprise both you and the mayor. She will then explain that the main problem is an entity called the Abyssal Seeker. She will then ask you to gather some of the council members excluding the mayor of Valeska and herself.
5. You will need to gather these members but in any order: The Fungasi Oracle, The Requiem Angel and the Grand Sage. The Grand Sage and Fungasi Oracle can both be found in Yggdrasil's Sanctum and the Requiem Angel can be found in the same place as before. Once you have gathered the other 3 return to Nightleach Graveyards and talk to the Elven Seer.
6. A cutscene will play were the Elven Seer teleports all of you to the Citadel in the Sky for a meeting. As soon as the cutscene ends, the citadel will shake and a bunch of Abysmal Creepers Lv 93 will appear. You will need to defeat 10 of them. They only use ranged attacks so strike them down with melee. After you kill 10 of them, 10 more will spawn and the Elven Seer will then tell you that they will just keep coming. The Fungasi Oracle, Grand Sage and Elven Seer will then teleport you, the mayor of Valeska and the Requiem Angel away to safety.
7. After being teleported to safety, the citadel will turn black and become corrupted. The Requiem Angel will then inform you that the Abyss has taken over the citadel and that you will need a special type of weapon to fend off against the monsters in there. She will inform you that you will need to gather her materials in order to make it. She will need 10 Corroded Wisps, 20 Celestial Tears, 5 Buckets of Dragon Dirt and a Skylight Contraption.
8. After forming the weapon, she will then hand it to you saying that you have wielded this weapon before. Knowing it's instrumental prowess, it's an Astral Vine Whip. Grab some food and gear before you talk to the Requiem Angel again because you won't be able to return unless you die. When you are ready talk to her again and she will teleport you up to the Citadel of the Abyss.
9. The Citadel of the Abyss is a giant maze so you will have to remember where you entered. You will first enter a room with 3 doorways. If you take the one in the middle, you enter a room with 3 Abysmal Axes Lv 75. They only use melee. The correct way to go is the door on the left. When you enter that door, an Chained War Demon Lv185 will appear and attack you. It uses melee and magic but is very vulnerable to Snow based magic. Pick up any valuable drops it leaves.
10. After killing the Chained War Demon, the Fungasi Oracle will then appear and inform you of the situation. After they teleported you, the Oracle, Seer and Sage got separated and lost the Citadel. The Oracle will heal you fully and imply that he is out of magic and can't assist you. There will be 2 doors, 1 south and 1 on your left. Taking the one south leads you back to the previous room so take the one to the left.
11. When you enter the next room, a cutscene will play where the Elven Seer will cast an Ash spell at you and you dodge it. The Elven Seer is being controlled by an Abysmal Parasite Lv 36. The Abysmal Parasite can't be damaged until the Elven Seer is tired out. The best strategy for this fight is to avoid the attacks and use ranged on the Abysmal Parasite. After defeating the Abysmal Parasite, the Elven Seer will thank you and inform you that the inner depths of the citadel are blocked by Abyssal Bushes which require level 90 Woodcutting. From here on only 1 door will show up other then the door you used to enter with an Abyssal Bush in the way. You will also encounter Abysmal Axes Lv 75, Chained War Demons Lv 185, Abysmal Creepers Lv 93 and Abysmal Wisps Lv 84 on your way to the core.
12. As soon as you reach the core, a cutscene will play where the Grand Sage is being controlled by an Abysmal Parasite with the Abyssal Seeker behind him. After the cutscene ends, you will be pushed out of the room by a magical force and the doors will seal shut. Attempt to open the doors and the Elven Seer will inform you that the Abyssal Seeker has locked them with an ancient abyssal magic preventing you from opening them normally.
13. Teleport out of the citadel and talk to the mayor of Valeska who will inform you that the cursed seal on the door is not an Abyssal magic but is Elven magic being used. Talk to the Elven Seer again and she will tell you that the type of Elven magic being used is a forbidden art that the Sage attempted and was banned from Elvaris. She will also inform you that you will need to talk to the Royal Guard near the basement of Elvaris Library for access.
14. Teleport to Elvaris and head to the library and a cutscene will play where the Royal Guard gets possessed by an Abysmal Parasite. The Requiem Angel will appear and exorcise the Abysmal Parasite away and place a holy ward around the library but she will inform you that you have 10 minutes to find the book before the ward disintegrates leaving the library vulnerable by abyssal infection. If the timer goes out, the library will go dark and you will die(this is a safe death). You will then be teleported back to the start of the quest, but you will still keep your progress. After finding the book, bring it to the Requiem Angel and she will teleport both of you back to the Elven Seer.
15. The Elven Seer will then tell you that inside the book's glossary is the ancient spell being used. Stock up on items. When you are ready talk to the Elven Seer and she will teleport you back into the Citadel of the Abyss. Follow the same path before and when you reach the sealed doors use the book on them and the seal will be lifted.
16. You will now need to fight both the Grand Sage Lv 168 and the Abyssal Seeker Lv 220. The Grand Sage will only use magic on you so attack with ranged and the Abyssal Seeker will use a shockwave attack when the Grand Sage is still conscious and will use an Abyssal Vine attack which does melee damage as well when he is unconscious. Despite the Abyssal Seeker being the main focus, focus on the Grand Sage first. The Abyssal Seeker does more damage when the Grand Sage is conscious. After finishing the fight, a cutscene will play where the Citadel returns to normal and the Grand Sage will thank you for your help.
17. Quest completed!