Board Thread:Wiki-Related Discussion/@comment-25491743-20180506124201/@comment-25926288-20180506190221

Agreed. Blood magic has always been "You and you are family and thus this is an unbreakable bond!" Always used to find family, grant access to family, etc.

Blood was used to---change one's form as seen by Nook via FGM wand and Tremaine, and Jafar; blood was used as "magic" symbolizing it as such when Regina helped the coven cast the curse.

From deleted scenes and canon scenes, we know that magic (black fairy dust in a deleted scene) in the form of a memory potion can be distilled from it.

Blood, hair, and tears....like the whole phrase "Blood, Sweat, and Tears".