Recently i started replaying Icewind Dale 2, and i found a feat i never really used before. Snake Blood. Is choosing snake blood making the character into something like a tainted one from third edition storywise? Or is it your yuan-ti ancestors of some kind affecting your blood. Is there any material to read on this?
Serpent Kingdoms is the best source for all things serpentine related.
I interpreted snake blood as you having yuan ti ancestry, but not enough to actually be a yuan ti.
Correct. Yuan-Ti have been known to interbreed with humans, so there are people with some heritage of those reptilians in them.
Outside of the game and the official rules for the feat, I also could see an alternate version that treats the character as naturally psionic and possibly give them 1 to 3 Power Points, given that Yuan-Ti are shown to have psionic potential.
As far as I know, Snake Blood doesn't explicitly relate to being a Tainted One or even a descendant of yuan-ti, but it definitely implies some sort of serpentine bloodline like your ancestors may have participated in some fraudulent rituals or have very ancient yuan-ti heritage.