 Why does Loy Chuk build an artificial environment for Ned?
Loy Chuk had flown his geological expedition out from the far lowlands to the east, out from the city of Kar-Rah. Loy Chuk's people had built their homes mostly underground, since the beginning of their foggy evolution. The mummy was taken to Loy Chuk's laboratory, a short distance below the surface. Ned Vince did not know how Loy Chuk had probed his brain, with the aid of a pair of helmets, and the black box apparatus. He did not know that in the latter, his language, taken from his own revitalized mind, was recorded, and that Loy Chuk had only to press certain buttons to make the instrument express his thoughts in common, long-dead English.
 He needs a habitat for Ned, so he can study Ned in a natural setting.
 He needs to keep Ned calm. If Ned believes himself to back in his own time, he will remain calm.  He realizes Ned is mentally unstable from the trauma of being brought back to life. He doesn't want Ned to commit suicide.  He needs a habitat for Ned until they can figure out time travel.  He needs a habitat for Ned, so he can study Ned in a natural setting.