- Transfer up to -50 health of any party member, into and up to +100 health to the caster.
- Range: 25m
- Conjuration time: 1s
- Requires active ability: Blood Magic.
- Arcane Warrior spellcasting: The spell can be cast with your weapon(s) drawn.
- The effectiveness of this spell does not diminish with higher fatigue levels.
- This spell only works on creatures with blood, as it makes a check for whether the target "can bleed" or not. This makes it ineffective on Shale or an undead servant raised with Animate Dead.
- This spell can be used on animals summoned by a rogue with the Ranger specialization. This mitigates the drawback of the spell as a ranger pet is much more expendable than a companion.
- Similar to Drain Life, this spell works against a target under the effect of Force Field, and actually does damage to the target as the damage is flagged as "unresistable". On the other hand, it can be resisted by spell resistance.
- Due to the way the calculations are set up, this spell will not do anything if the caster is at full health, although it will still be put on cooldown.
Blood Sacrifice is a difficult spell to use unless you've thought about it in advance when constructing your party. If the blood mage has the Heal spell then you can take health from a party member that can afford it and then heal them back up as a way around the blood magic healing debuff (though it may be simpler to cancel Blood Magic and cast Heal on yourself). The sacrifice gives you twice the health it takes from your companion so it is a net gain to do this.
It can also be a useful emergency button if you've overdone it on the blood magic spellcasting and an enemy is bearing down on you at low health.
The best targets for this spell besides ranger pets are usually warriors that are not currently tanking something, as they have decent constitution and armor so are least likely to get in trouble from it.
This can also be a more reliable way to manage a Reaver in the party. Blood Sacifice can be used to get the Reavers health lower, and the health gained by the mage can be used to use spells such as Regeneration or Heal later to keep the Reaver near-death, but alive and dealing extreme damage.
Having two blood mages with Blood Sacrifice in the party will allow them to cast the spell on each other simultaneously, and in net both are healed by 50 points negating all needs for aforementioned "blood batteries".
Thanks to Blood Sacrifice, the main character or Wynne as a Blood Mage/Spirit Healer makes an extremely effective support character. The character can heal the party using Blood Magic, replenishing themselves with Blood Sacrifice from the highest health party member as needed. Because Blood Sacrifice and the various healing spells impart more health than they use to cast, this method can multiply your 'mana' pool many times over. An added benefit is that since this type of character uses Blood Magic (and not their mana) almost exclusively, they're free to maintain several high cost sustained abilities, such as Haste, since these still reserve Mana even when using Blood Magic. With proper use of tactics this can even be reliably automated (so long as you avoid bloodless companions such as Shale).