A short notes for achievement hunters
The achievement is "Pruning the Sky Garden",which gives the title"Skyjack".
This pretty annoying achievement requires 10 kills of the last boss in its 3 different versions(for a total of 30 kills), only problem is that the last boss its semi random so,you can happen to have 10 kills with the 2 types of him but still missing the third because randomness its against you.
I noticed that last boss's spawn its not completely random, but it depends on the third boss.
There's are 4 bosses (not including the secret one):
First : Duke / Karasha / Terkasia (its doesn't matter which one spawns)
Second: Giant
Third: Dragon / Skeleton / Firmbrisk
Fourth: Valtryssir / Mektryssir / Adryssir (Dracoliths)
So to make this short and simple:
If the third boss its the Dragon then the fourth boss will be Mektryssir
If the third boss is the Firmbrisk then the fourth boss will be Adyrssir
If the third boss is the Skeleton then the fourth boss will be Valtryssir
This means, if you only need for example Valtryssir but if at the third boss you get the dragon or the firmbrisk, you may as well /reset the instance right away since last boss won't be the one you need.