What the achievement asks
Defeat 10 of the 22 special encounters across the Isle of Dorn. Five points, account-wide.
Ten, not twenty-two. The list below is a menu rather than a checklist, and that changes how you should play it: take whichever rares happen to be up as you fly past, and stop the moment the counter reaches ten. There is no reward for clearing the island.
Where they are
| Rare | Coordinates |
|---|---|
| Rustul Titancap | 35.8 74.8 |
| Sandres the Relicbearer | 62.8 68.4 |
| Springbubble | 58.6 60.6 |
| Warphorn | 57.0 34.6 |
| Bloodmaw | 41.8 76.2 |
| Emperor Pitfang | 47.8 60.2 |
| Plaguehart | 50.8 69.8 |
| Gar'loc | 53.6 79.8 |
| Escaped Cutthroat | 25.8 45.0 |
| Tempest Lord Incarnus | 57.4 16.2 |
| Kronolith, Might of the Mountain | 48.0 27.0 |
| Shallowshell the Clacker | 74.0 27.6 |
| Twice-Stinger the Wretched | 57.0 22.6 |
| Flamekeeper Graz | 64.0 40.6 |
| Clawbreaker K'zithix | 55.6 27.0 |
| Alunira | 23.2 58.4 |
| Zovex | see below |
| Kereke | 30.8 52.2 |
| Rotfist | 30.8 52.2 |
| Tephratennae | 73.6 38.8 |
| Sweetspark the Oozeful | 69.8 38.4 |
| Matriarch Charfuria | 72.6 40.4 |
The one without a fixed spot
Zovex is the exception to the table. He has no fixed spawn point in Wowhead's zone data, and players find him wandering rather than waiting. Since you only need ten of twenty-two, the sensible answer is to ignore him and take one of the others.
How to actually find them
Rares here are on individual respawn timers rather than a shared rotation, so at any moment a handful of the twenty-two are up and the rest are not. Two habits make that work in your favour.
Fly the list rather than camping one name. A lap of the coordinates above will normally turn up more than ten live rares in a single circuit.
Use a rare-scanning addon or the group finder. Players list groups for Isle of Dorn rares constantly, and joining one puts you in a shard where somebody has already found something.
Most of these die in seconds to a modern character, so this is a travel problem rather than a combat one.
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. The treasures of Treasures of the Isle of Dorn are on the same circuit.