As the name "first danger" suggested, the fighting style was about fast reactions to the first appearance of an enemy and be the first danger to the same.
The majority of drow combat groups, especially scouting groups, had at least one user of this style among them. That individual's role was to react fast and shoot a poisoned bolt to incapacitate an enemy before combat really began.
The style gave fast reactions and was certainly useful at the start of combat but, due to being almost useless in prolonged combat, users also tended to learn other styles to give themselves other offensive abilities.
Drow society was one in which vigilance was paramount, and thus the basics of this style were part of the standard curriculum of every drow fighting academy.
This style is based on the Improved Initiative and Quick Draw feats of 3rd-edition Dungeons & Dragons.