This quest is not available in game.
Claim your reward from Hydraxis' Coffer.
<name>, your services to the Warlords surpassed all we could expect from the denizens of this world.
We do not understand your people's notions of gratitude, or rewarding good works, but in this case... perhaps a reward is warranted.
Under the surf at the southern base of this island, you will find a coffer. In it you will find your... reward.
Go, <name>. Claim your reward.