Ok so here's my question. Nightwing manages to KO Dr fate. Does Nightwing still get mystics damage? or is he safe already? Which goes first, being KOed or the mystics effect? Thanks in advance! :-)

Mystics triggers when the character takes damage. Once triggered, nothing stops it from resolving.

Rule book pp. 13
Rulebook pp. 15-16
KO occurs before the resolution of the attack.
Mystic damage is dealt after the resolution the attack.
Mystic Damage can't delt because the character has been KO before it would be delt.

Edit: apparently I'm wrong and I can't find the delete button.

Copy that. Guess it still seems to work like before. At least that part of mystics didn't change. Thanks again! :-)

You can just edit your answer, delete what information is incorrect, and say something to the effect of "ignore this" or "nothing to see here" as it's common.

To your credit, you did a great job in quoting, but you missed the last one on page 9:

"After Resolutions triggered effects. After resolutions triggered effects wait until the current action or special triggered effect has fully resolved to begin resolving itself."
"An after resolutions triggered effect will resolve once triggered, even if the power or ability that granted the triggered effect can no longer be used or is lost. (See p. 29 for Can’t Use and Lost.)"