I searched for this phrase but didn't find it any where "where are those brave warriors;"the turn of the time has rendered all of them low and powerless.Does it mean"change of time"? Also what is being "low"referred to?
It doesn't seem to be an idiom in English - or at least not one that Google recognizes. Without more context it's hard to tell what it means exactly - but my guess would be that it's analogous to the phrase the turn of the century:
the time when a particular century ends and another begins
So in the broad sense, "the turn of the time" would mean "the time going forward; the progression of time".
As to your other question, "low" can mean "unhappy, exhausted" (as in "he was feeling a bit low today"). So those people would be sad and lacking the energy.