Survival Thermal vision NON-Human

Due to spending so much time in a Pitch black environment your body has adapted and created a second eyelid  which allows you to see thermal heat signatures. The eyelid gives the eyes a milky appearance. 

  You can now see heat and its lack from nearly any distance, distinguishing different heat levels as gradients of grey, from black (extremely cold) through grey (mildly warm) to white (scorching hot). it will also work underwater to a reduced range of 30 feet. This ability can be activated by focusing your vision and closing the second eyelid. 

Advantage on perception checks, advantage on footprint\traces related survival checks.

If the sight is being used  when something  of extreme heat is triggered (ie: fireball, Wall of fire and the like ) a saving throw of DC12 must be passed or temporary blindness for 1-4 round to allow the eyes to adjust bright light does nothing to eyesight if thermal lids are being used as it is light and not heat.