You may need to kill the Swirlspine Guardians in the area around Phinigel in order to make this mob spawn.
She helps adventurers working on their epic quest to get their drop from Phinigel Autropos.
You say, 'Hail, a harbinger of the seas.'
a harbinger of the seas looks through you and brushes her flowing hair to one side. It swirls and sways like sea kelp in the frigid waters. 'Phinigel Autropos, the last of his kind, child of the Ocean Lord Prexus, is not here. However, he will return for you if you wish it. Are you [prepared to face Phinigel]?'
You say, 'prepared to face Phinigel'
a harbinger of the seas proclaims loudly, a great churning, gurgling sound nearly drowning out her natural melodic timbre, 'A challenger seeks to test her mettle against Phinigel Autropos!'
Phinigel instantly appears and aggros. Once dead, he only drops the required epic item.
If the person hailing is not doing the epic quest :
a harbinger of the seas looks through you and brushes her flowing hair to one side. It swirls and sways like sea kelp in the frigid waters. 'Phinigel Autropos, the last of his kind, child of the Ocean Lord Prexus, is not here. Perhaps he will return.'