Find and speak to Captain Vilethorn north of the Quel'Dormir Gardens.
Use Wavespeaker Tulra's sea horse to reach the forward post quickly.
The Captain used the information you gathered for him to make a forward post under the terrace to our west. He's been preparing there for some kind of attack against the naga.
You should go to him immediately and inform him of the scope of what you've witnessed. Our force is small, and I fear for our soldiers if we charge in too recklessly.
Take my sea horse. It knows the way.