Observe as Earthmender Duarn attempts to speak with Nespirah.
Speak with Earthmender Duarn
A trained shaman has the ability to communicate with the four elements of earth, fire, air and water. This is known.
What is not as widely known, however, is the presence of a fifth element. This element is not as clearly described as the other four, but it has to do with the shared... commonality between all living creatures.
My theory is that the crab, as a creature of the sea, is close enough to Nespirah that, with the elements' coaxing, we can convince it to act as Nespirah's mouthpiece.
I had assumed that the naga were only here for those pearls. No, this makes much more sense. If they had Nespirah's power under their control, the amount of damage the naga could do would be catastrophic!