What the achievement asks
Complete the Siege on Dragonbane Keep scenario. Ten points, account-wide.
Not win a race, not hit a target, not survive anything. Be present when the siege finishes.
Getting in
The scenario unlocks at Renown 5 with the Valdrakken Accord. When you reach it, a small dragon flies up to you somewhere in The Waking Shores and offers To Dragonbane Keep!, which points you at the staging area at 30.51 77.91.
If no dragon has found you, fly to the coordinate anyway. Several players report reaching Renown 7 without ever being approached, and the event works perfectly well without the introductory quest.
The siege runs on a fixed schedule, announced in the zone before it starts: an on-screen warning tells you the siege is about to begin, and the event itself takes roughly fifteen minutes across its stages.
What you actually have to do
Turn up, follow the crowd through the stages, and be there at the end. The scenario is designed to be carried by whoever happens to be in the zone, so there is no role to fill and no minimum contribution.
There is not even a level requirement. One player picked this up on a level 5 character who wandered into the event area, helped the caravan along and got both the achievement and the Dragonbane Keep Strongbox at the end, the box needing level 60 to open but the achievement landing all the same.
Do the other two on the same run
While you are inside, the three tablets of Chiseled Record are a two-minute detour, and Snack Attack can only be worked on during stage 1 of this same event. Going in for one of the three and coming back twice more is a waste of a schedule you do not control.
Where it fits
Part of Across the Isles, which rewards the Stormtouched Bruffalon and is itself a piece of A World Awoken.