It took weeks of searching, but I finally caught a glimpse of Wali al Aswad. I knew I was getting close when I found a series of fulgurite formations this morning, and sure enough, I spotted several wyverns later in the afternoon with a lone rider among them.
The rider clearly saw me too, because soon enough the wyverns were circling overhead. I waved and yelled in greeting, even calling out Mei Yin's name just in case. Yet without so much as a nod, the wyverns regrouped and flew off.
Wali's not a social butterfly it seems, but I'm not letting them off the hook that easily.