There was the following sentence in the article of Time magazine, titled “Your brain in a shootout: Guns, fear and flawed instincts” dealing with the brain’s function in a life-or-death situation. As Jim Glennon, a lieutenant in the Chicago Police, found himself placed in, one autumn day in 2004 when he was assaulted by a gun-shooter:- http://swampland.time.com/2013/01/16/your-brain-in-a-shootout-guns-fear-and-flawed-instincts/
“As happens for most people in life-or-death situations, his brain began to manipulate his perception of time, slowing down the motion as he fled down the corridor. But for each superpower his brain gave him, it took one away. In a flash, his brain reprioritized, shifting finite resources to the cause of survival.
I’m not very clear with what the line, “it took one away” means? What do ‘it’ and ‘one’ represent? Is ‘it’ a substitute for his brain or ‘a superpower’? Is ‘one’ “one of those superpowers” or “him”?
What does 'for" of 'for each superpower' function for? Is it grammatically or rhetorically wrong, if I take ‘for’ away from the line, and say “His brain took away each superpower it gave him”?
How can I rephrase it in a clearer way, without using substitutes, “it” and “one,” (even if the end result includes redundant expressions)?