It is easy to get the Crazed Karka Queen Killer, you'll find an island control on the upper right, you need to finish the secure settlements reach to 4/4, and then you'll get the Karka Queen at once.
And the four dynamic places are marked in the below map:
After completion of the four dynamics, Karka Queen will appear in this dynamic here below:
First, come to the pearl islet, and find out the NPC, then you'll enter a mode like in a personal content. You will have to escort a dolyak through a 5 minutes path with a lot of local wildlife (a lot of skelks too). At the end of the escort, there will be a cutscene with a plot twist. Stay until you get the Contractually Obligated achievement and then you can exist on the instance. Or you can repeat the instance to farm the skelks if you like but the magic find buff wears off inside the instance.
The two achievements are the last two locked in The Secret of Southsun, and which do not need you spend any Guild Wars 2 gold to get them. What you need to do is just follow us and find the correct guide to get the two achievements as soon as possible.