Constancy Relics are found in the lower half of the first section of the Tziah Block within Tartarus. They may be found in groups with other shadow types present. In The Answer, they can be found in the first section of Caina within the Abyss of Time.
Constancy Relics appear in B1F and B2F of the Secret Laboratory within the Midnight Channel. They will attempt to affect the party with Anima Freeze before attacking. Upon being defeated, they may drop the Stone Hide material. Selling 4 Stone Hides at Daidara will unlock the Bucking Broncos weapon for Chie Satonaka in the shop.