The Seal of Orichalcos

[[Lore::This card is unaffected by the effects of Spells, Traps, and Effect Monsters. The activation and effect of this card cannot be negated except by an "Orichalcos" effect, or if the opponent controls "Legendary Knight Critias", "Legendary Knight Hermos" and "Legendary Knight Timaeus". As long as this card remains face-up on the field, this card controller's monsters gain 500 ATK, and are treated as DARK monsters, in addition to their normal Attribute. This card's controller's Spell & Trap Card Zones are also treated as Monster Card Zones. However, monsters in the Spell & Trap Card Zones cannot be declared as an attack target unless their controller's Monster Card Zone is unoccupied. If this card's effect is negated, destroy all Monster Cards in your Spell & Trap Card Zones. The Fusion effects of "The Eye of Timaeus", "The Fang of Critias" and "The Claw of Hermos" are negated when this card is activated. If "Legendary Knight Critias", "Legendary Knight Hermos" and "Legendary Knight Timaeus" are face-up on this card's controller's side of the field at the time of activation, they are automatically destroyed and sent to the Graveyard.]]