What do you call Alphonse Elric's armor seal? The circle Ed made to attach his brother's soul?
What do you call Alphonse Elric's armor seal? I have yet to read or watch this series but the answer can be found here. Apparently, a soul can be bound to inanimate objects via a Blood Rune.
A Blood Rune, also known as a Blood Seal (血印, Ketsuin), is an alchemical technique used to bind someone's soul to an inanimate metal object. The iron in the blood will interact with the metal it is on, causing the object and the blood rune to form a symbiosis.
In exchange, Ed gave up his right arm and used his own blood to successfully bind his brother's soul. The blood rune can be seen in Al's body.