illuminate

One candle - all it takes; 

illuminate a room

filled with darkness

One breath - all it takes;

  extinguish a candle

plunge a room into darkness

left to the mercy of the dark

One match - all it takes; 

relight the candle

take control of the darkness

But one breath - still all it takes;

extinguish the candle

plunge a room into darkness

And so it continues:

light, dark, light, dark

No victor, only a smaller loss. 

A constant struggle;

In the end everyone gets burned

Impossible to escape - an iron grip. 

impossible to win or lose. 

Good and evil struggle for eternity. 

fight for eternity. 

Evil and Evil struggle or eternity

fight for eternity. 

Good - thrive for eternity

peace for eternity.