You can get either Deductive Mind/Captain Obvious
achievement or Fine Investigator
Speak with Sunkiest
For Deductive Mind achievement do this:
While speaking to Sunkiest
choose: Lizards did it!
To get Captain Obvious achievement
choose: ORCS DID IT
Only 4 clues are enough, here are they:
For Fine Investigator achievement do this:
Find 5 more clues, 9clues in total needed for this achievement!
Come back to Sunkiest
to finish the quest