GA pilot in the traffic pattern at nighttime reported Tower extended their downwind toward an unlit mountain peak which they were aware of but could not see.

Narrative

I was performing my night currency and on the last of 3 stop and goes. ZZZ Runway XX was in use. A few miles out directly in the approach path to Runway XY lies the unlit obstacle; listed at 6178 feet on the sectional. On left downwind; ATC extended my downwind. At TPA; I would have collided with the hill as I could not differentiate it from the inky black night sky. I patiently waited for ATC to call my base. When they did not; I turned left approximately 30 degrees and advised ATC I was turning to avoid terrain. ATC instructed me to return to original heading and to climb if necessary to avoid terrain. I complied and climbed to 7000 ft. to make sure I had adequate clearance.I think this obstacle is a hazard in the approach path of runway at ZZZ and that ATC should refrain from using it at night. I believe that in that particular situation I made the right call to deviate laterally rather than rely on my climb performance so close to the terrain. ZZZ is a primary training airport and many new pilots train there. The existence of extended downwinds over obstacle is a serious hazard at night and that the ATC should be more cognizant of the risks of mountain flying in and around rising terrain.