Defeat 5 Servants of Neptulon. (You must be in naga form when you defeat them.)
If you lose your Slitherblade Trident, speak to Valishj.
If you lose your Slitherblade Charm, speak with Korrah at Ethel Rethor.
Neptulon's minions have arrived here and are doing all they can to thwart us. Clearly, they've discovered our motives.
This only confirms my suspicion that what we seek is indeed somewhere in these ruins!
These water elementals are no match for our forces! Take this trident and use it to destroy the worthless servants of the Tidehunter.
When we find what we seek here, Neptulon himself shall fear for his life!