I finished this achievement, with a slight variation to those above...
Quick version: dominate a wild Graug, and use Dragon Song to summon a Drake... Being a summoned mount, it won't fight back making taking it down very quick and easy...
Longer version:
- You'll need to have completed all the Carnan quests, to unlock the Dragon Song skill... As a result, this method is probably best for those near completion, and looking to mop up the last few achievements, so wouldn't recommend it on a fresh start...
- Fast travel to the Haedir located in the South West corner of Seregost (over looks the Ice Plans to the left of the map)...
Every time I travelled here, a Graug spawned just north of the Haedir tower, close enough to see on the mini map... Other guides mention a Drake spawning near here, which I didn't have any luck with after 10ish "Advance Times" unfortunately , so found this method worked a treat...- Head to the Graug, weaken then dominate it, then mount up and travel out to the far reaches of the Ice Plans
- Summon your Drake, then go to town on it with your bow (charged headshots will kill the Drake the quickest)
Any suggestions to improve or flesh out this guide, let me know