During our travels in Hallowfall, a side quest explains the whereabouts of the expedition's last mage — and why the Arathi fight so hard to defend their new home.
After our initial jaunt through Hallowfall, General Steelstrike offers a few requests for aid of less urgent consequence than the main story, but ones with just as intriguing of premises. One such request is the desire to check in on a mage in the area — The Last Mage in Hallowfall. According to Steelstrike, everyone but him has given up hope of returning home via a portal, and being the pragmatic type, she wishes for us to give him a reality check.
As we reach the mage's home, we quickly see him in the midst of his arcane experiments, with arcane-infused crabs teleporting around erratically. While Wenren himself seems plenty tossed around, he is equally thrilled at what seems to be teleportation of his own doing.
Upon reaching him inside, he is rather shocked, but rapidly ropes the player into his experiments as well, tasking us with extracting arcane-infused organs from the local crab populace.
Before you depart, you can speak to him on a number of matters regarding his status as a mage, as well as the nature of his current experiments. For Mage players, additional dialogue options are also available, showing your expertise in the craft he seems to be mildly fumbling with.