Theory about use of Feruchemy on Threnody.
On Threnody, one cannot spill the blood of another (visibly, at least) because that enrages the shades.
What if a Feruchemist used Aluminum to store all of their identity away? The Feruchemist then has no identity left. Then, when the no-ID Feruchemist attacks someone and draws blood, well, the victim is attacked by "no one." "Nobody" drew blood. Fly under the Shades' radar, Odysseus-style.
Identity Feruchemy could be used other ways, too. Say, for example, a surgery needs to be performed. Drain the identity of both the surgeon and the patient, then they both share the identity of "nobody". They are practically identical. That will fly under the Shades' radar, because Shades are triggered specifically by a person drawing the blood of another; a person spilling one's "own" blood has no effect on shades.

















