The spilling of blood can unleash significant magic power, and many cultures have developed ways of accessing that power. Some can use magic powered by inflicting significant wounds to curse their enemies.
Blood hexes take many forms, but all obey some basic rules that apply to each blood hex feat. Blood hex feats are available to any character who meets the feat’s prerequisites. Blood hex feats work only against targets you have dealt hit point damage to recently, with the exact time frame and any requirements for how you deal the damage outlined in each feat. The saving throw DC of a blood hex is always equal to 10 + 1/2 your character level + your Intelligence, Wisdom, or Charisma modifier (whichever is highest). You can target a creature with the same blood hex at most once every 24 hours, whether it is affected by the blood hex or not. You can use a number of blood hexes per day equal to the number of blood hex feats you have, plus one additional use per day at 4th level and every 4 character levels thereafter. You can use the same blood hex multiple times, as long as you don’t exceed your total uses of blood hexes for the day.
Shamans and witches can take a blood hex feat in place of a regular hex and sometimes gain additional effects when they use a blood hex, but must still deal hit point damage to a creature in order to use the blood hex. A shaman or witch can use blood hexes an unlimited number of times per day, but still cannot target the same creature with the same blood hex more than once every 24 hours. All blood hexes with a duration of 1 round can be extended normally using the cackle hex or the chant hex.
The effects of a given blood hex doesn’t stack with themselves, even if the blood hex is used by different sources, but a creature can be cursed with any number of different blood hexes at one time. A blood hex is a supernatural curse effect, and counts as a hex for the purposes of abilities that work against hexes.
Pathfinder Player Companion: Magic Tactics Toolbox © 2016, Paizo Inc.; Authors: Alexander Augunas, Steven T. Helt, Thurston Hillman, and Ron Lundeen.