Once you complete the questline to unlock the Man’ari Eredar customizations for Draenei, there will be six different NPCs spread across Argus with the title “Ally of Arzaal”.
Besides the flavor they add showing that there are now more Man’ari Eredar allied with us, they will also give you one Argunite Cluster. Argunite Cluster contains 10-15 Veiled Argunite and a number of Argus crafting materials that can be used to buy cosmetics unlocked by the questline.