Return of Reckoning

im not sure that i can follow your lead. What other quest? There is no other quest that specifies on killing Thar'ignan besides the one where you have to kill him 4 times for the shoulders. And im pretty sure there must be plenty of players who finished that one whilest gearing up, therefore some should have stumbled on the follow up quest for "liquid serenity"?

He is required for Stalwart Soulstones and for the speedrun. Besides that no quest seems to mention him dircetly.

I agree that there will be some chain. And all i want to know it where to pull in the first place. Thought someone discovered it already. And it would be worth mentioning in the wiki, isnt it?

I have found it as part of a chain quest for the fleshborne ring quests.

Destro - Infinite Patience
Order - Portal of Rage

Available from the mysterious knight outside of Kaarn's room once the above chain quest is completed

The Liquid Serenity should now be properly attainable by all as part of today's Bastion Stair updates - let us know if anyone has any issues after today's patch.