Larian Studios Forums Divinity: Original Sin 2 Divinity - Original Sin 2 - General What is source?

It seems to be 'Animating Life Force'. You can find it gathering in places as a liquid, and using this kind of Source empowers your spells and abilities (Aleroth used it for healing). When Source is inside a person it is effectively their Soul, since you can do terrible things like rip the Source out of someone and make them stop existing / no longer able to go to the Hall of Echoes. Or enslave people by taking their Source.

But you can also add more Source to an already living thing, which gives you immortal wizards. Or keep Source inside a corpse (or soul jar) so that they continue to be animated even after death as Undead. Or pump them so full of Source they become a weapon.

The short answer is that "Source Magic" is Divinity's version of Blood Magic, or Black Magic, or Forbidden Magic. I.E. it's just another school of magic that's more powerful than regular magic in-lore, but pretty indistinguishable in-game. And it's called Source Magic (a very poor descriptor) primarily for the sourcery pun and Pratchett reference.

Source magic seems to be some kind of soul magic. You could do it with your own soul, but reaping souls from others lets you get stronger much faster obviously.