Hint: Like all other Job Change quests, this has to be done while you are not in a party. Bringing a friend along (especially someone that can heal) while keeping yourselves not partied will greatly decrease the difficulty of the Quest chains.

PART 1
Talk to NPC Brayden, located at the northern part of Etton. Inquire about the Giant Warrior: Berserker Quest.

PART 2
Brayden will instruct you to unseal the Violent Devil Crow, sealed in Stone somewhere around the giant statue in the region of Kowarre. These Stone statues are hard to locate, but there are two possible locations for the Statues.

Hint #1: Upper rightmost corner of H3.
Hint #2: Very middle of H3, right beside boulders.

Once you have found the Statue, double click on it to Unseal the Monster inside, defeat it and report back to Brayden.