All fights are matters of life and death.  
I've had dreams where sometimes I stay and fight, and sometimes I run...usually against overwhelming odds, like 30' generators hitting me with lightning bolts and paralyzing me.  That was the worst nightmare I recall, and even then I was almost stronger than the electricity.  I defied it to the point it almost killed me...so to speak.  This was in a futuristic setting where a flying saucer would be right at home.  (Too much TV!!!   )
I have never fought anything like Nazcul or cave trolls in these dreams.  I think I would be prepared for them if they ever showed up in a dream.  Don't know if I'd run or not.
Les