What the achievement asks
Collect all twelve Citrine gems on the Siren Isle. Ten points, account-wide.
The twelve, and where each one comes from
| Citrine | Source |
|---|---|
| Windsinger's Runed Citrine | The Reforged Anew questline, from Angorla |
| Mariner's Hallowed Citrine | Kills, chests, or bought from Apprentice Tanmar |
| Roaring War-Queen's Citrine | Kills, chests, or bought from Taljori |
| Thunderlord's Crackling Citrine | Kills, chests, or bought from Didi the Wrench |
| Old Salt's Bardic Citrine | A triggered event, reported from The Drowned Lair |
| Stormbringer's Runed Citrine | A triggered event, reported from Shuddering Hollow |
| Fathomdweller's Runed Citrine | A triggered event, reported from Shuddering Hollow |
| Undersea Overseer's Citrine | A major excavation, reported from The Drain |
| Storm Sewer's Citrine | Reported from The Drowned Lair |
| Squall Sailor's Citrine | Reported from The Drain |
| Seabed Leviathan's Citrine | The weekly quest Serpent's Wrath |
| Legendary Skipper's Citrine | The weekly quest Tides of Greed |
The event sources are where individual players got theirs rather than fixed rules. The excavations and triggered events all drop citrines, and which one you get is not something you can steer.
Two of them will not credit from a vendor
The Seabed Leviathan's Citrine and the Legendary Skipper's Citrine are the two people get stuck on. Buying them from Taljori gives you the gem and no achievement credit.
The criteria only ticked for players when they completed the matching weekly quest: Serpent's Wrath for the Seabed Leviathan's, Tides of Greed for the Legendary Skipper's. Those two weeklies belong to the Naga and Pirate invasions respectively, so this achievement inherits the isle's three-week rotation whether you like it or not.
Both are also on the list for Siren-ity Now!, so you were going to do them anyway.
War Mode appears to help
Multiple players report a much higher citrine drop rate with War Mode on, some describing it as close to guaranteed. That is a player observation rather than a documented rule, but the cost of trying it is small and the isle is not a dangerous place to be flagged.
Contributing to the excavations at the same time seems to matter too, and it is Excavation Projects in the same branch, so there is no reason not to.
Where it fits
One of the pieces of You Xal Not Pass, which rewards the Shadow of Doubt mount and is part of Worldsoul-Searching, the War Within meta.