Blood! is a modification for Quake made by Kevin Bowen. Instead of a single set of blood particles appearing when a Monster or The Player is hit, this modification shall make it so that five particles overlap with each other, resulting in more visible blood.
Kevin Bowen argued that this modification enhanced the realism by making the game bloody, but did not go over the top as "gore" and "violence" patches are apt to do. He felt said modifications lost their novelty quick and also killed suspension of disbelief.
Blood particles after the mod is added.
Blood particles in the vanilla game for comparison.