Blood Magic
For the support gem, see Blood Magic (Support Gem).
Blood Magic is a keystone passive skill.
Skills that reserve mana will now reserve life.
Eldritch Battery will not give you back your mana, it will merely remove your Energy Shield.
When combined with Chaos Inoculation, casting a spell will kill the player instantly.
Casting a spell that would reserve 100% of your mana with this keystone will also kill the player instantly. For example Spell Totem + Determination (250% cost increase of a 40% reserve aura for a 100% reserve cost, which will reserve all your health)
Related Items
The Covenant allows to use Blood Magic without the keystone.