Here a list of Side quests and Factions quests listed alphabetically.
There is a Task called Hearts of Chaos where you have to turn in the Chaos Hearts you get for closing a portal, to Agarth.
This task is actually a quest because when you close all 25 portals and turn in the hearts, the achievement progress moves.Edit: Oct 30, 2022 - Some people are saying you don't have to close all 25 portals and the achievement unlock for them.If you choose to lie and keep "Maisie's Ring" in the relevant quest, as opposed to returning it to the quest giver, the quest will mark as completed but not count towards this achievement.
Thanks to Niku no Nioi for pointing this out. This is probably why it didn't unlock for me on my first play through because I remember keeping the ring on my first play through and giving it on the second play through.
If you're doing a second play through, be extremely careful not to explore and do too much and only do/accept quests when a quest giver is available.
Side Quests:A Small Favor
An Old Bond
Beyond the Barricades
Chaos Matter Delivery
Crafting Made Simple
False Prophets
Guard Down
Headhunters
Invasive Species
Ivan's Favor
Last Breath
Lesson of the Bones
Listening to Echoes
Lone Survivor
Lucky Charm
Night Barghest
Of Life and Death
(This is the quest you need be be very careful about. You should only accept it from the quest giver. If it is triggered by entering a house, etc. you should reload your last save otherwise it may cause this achievement to glitch for you as it did me and several others. Hopefully they will release a patch to fix it. I've provided a link at the bottom of the guide)Outcast's Revenge
Playing Crownhold (Directly after the Preparations quest)
Preparations
Rat Plague
The Cursed Grove
The Giant Killer
The Raid
The Sound of Mithros
The Stolen Ticket (Easy to miss quest - see link below)
The Taken
The Tree and the Branches
The Unbound
Faction Quests:A Preordained Encounter
Lyenna's Lullaby
Mysterious Monoliths
Here's a link to guide for the Tree and the Branches quest. This quest doesn't have markers of where you need to go to collect the armor pieces.
https://www.reddit.com/r/kingdomsofamalur/comments/rk0no2/zy...Here's a link for a guide to the Lessons and Bones quest. You will need this armor set for the Black Hole achievement.
https://gameplay.tips/guides/kingdoms-of-amalur-re-reckoning...Stolen ticket (easy to miss quest)
https://kingdomsofamalur.wiki.fextralife.com/Stolen+Ticket#:...,XP%2C%20loot%20and%20other%20rewards.
Of Life and Death (This quest can cause this achievement to glitch if not done properly)
https://kingdomsofamalur.wiki.fextralife.com/Of+Life+and+Dea...