The core "Guardian" monsters were initially released in Dark Crisis and re-released in Dark Revelation Volume 1. They can only be Summoned if their corresponding Equip Spell Card is already face-up on the field. However, they can still be Set without controlling their respective Equip Spell Card. The Equip Spell does not have to be equipped to their corresponding monster, and due to their Summoning conditions, usually cannot be. "Guardian Eatos" is the only one of the "Guardians" with an associated Equip Spell Card who can be Summoned without restrictions.