You've spent time exploring in harsh climates with sweltering days and freezing nights. The effects of Extreme Heat on you are reduced by one level.
You're used to going a long time without rest or rations. At Level 12, effects of Exhaustion on you are reduced by one level. (The first level of exhaustion has no effect, and all other effects of exhaustion including death are moved one level higher. This effect stacks with other features that reduce exhaustion.)
Your keen eye isn't fooled by mirages or illusions. Starting at Level 22, you have advantage on Perception and Insight checks to see through Illusions, both natural and man-made.