What the achievement asks
Finish Keeper Tyr's story, from his fall to his return. Account-wide, and it grants the title of the Tyr's Guard.
Why the quest is not where you expect
This is the achievement people ask about most, and almost never because it is bugged. Tyr's story is not one questline: it is four chains released across three patches, and the achievement only ticks when the last quest of the last chain is turned in.
Each chain hides the next. If Valunei has nothing for you in Thaldraszus, it is because something earlier is unfinished, not because the quest failed to appear. Work backwards through the four below and you will find the gap.
The four chains, in the order the game wants them
| Chain | Starts with | Where | What gates it |
|---|---|---|---|
| The Silver Purpose | The Silver Purpose | Keeper Tyr, Thaldraszus 60.4 58.6 | Renown 12 with the Valdrakken Accord |
| Tyr's Fall | Silver Mettle | Nozdormu, Thaldraszus 60.4 58.8 | The Silver Purpose |
| Reforging the Tyr's Guard | ends at A Sliver of Silver | Follows on from Tyr's Fall | Tyr's Fall |
| Tyr's Return | Data Recovery | Valunei, Thaldraszus 60.8 63.6 | Everything above, plus the side quest below |
The last quest of the last chain is Logotyrapy, and turning it in is what awards both the achievement and the title.
The side quest that stops everyone
Before Data Recovery will offer, you need An Exemplar of Compassion: Valunei, a standalone side story in The Azure Span at 17.6 31.4. It is not part of any of the four chains and nothing points you to it.
Skip it and Valunei simply does not appear in Thaldraszus later. That is the single most common reason a player who has genuinely done every Tyr questline still cannot start the final chapter, and it is worth flying out to 17.6 31.4 to check even if you are fairly sure you did it.
Wowhead sometimes shows it as completed because an alt did it. The requirement is per character for this step, so trust your own quest log over the green tick.
If you are returning after a break
Search your quest log and your completed quests for anything with Tyr in the name. The game is generous about credit here: a player who did the Tyr's Fall chain back in its own patch and stopped will find that once The Silver Purpose is done, several later steps skip themselves and the chain jumps straight to Data Recovery.
None of this is difficult content. There is no group requirement, no farm and no randomness. The whole thing is story quests at your own pace, and the only real cost is the Renown 12 gate at the very start, which arrives on its own while you do anything else in Valdrakken.
Where it fits
One of six under Dragon Quests, a piece of A World Awoken. The Renown 12 it needs is the same renown tracked by Friend of the Dragon Isles, so doing that one first clears this gate without extra work.