Although Eywa may witness the events within her own ecosystem, she cannot see what lives outside of it. To this end, Eywa is blind to humans, and she can not see her animals when their "thoughts" have been altered. Thus, the chosen Na'vi must be the so-called "eye and hand of Eywa". By interacting with Eywa's roots, the Alaksi Nari can commune with her.
The role of these Na'vi is recorded in their oral history. The account describes a brave hero in the service of Eywa, where with his task complete, he returned her tools to her. Henceforth, Eywa encompassed these tools within living chests, waiting for the time when another ready eye will need them.
- James Cameron's Avatar: The Game NDS - Ingame Pandorapedia article