Four Horsemen Rule

The Only one copy of any card, except basic land
does not apply to cards that are self-reverentially
interact with other copies of the card.
Cards that allow action with a copy of that or
anther specific card in another zone of them.
(Llanowar Sentinel; or Dark Supplicant & Scion
of Darkness)
Cards that interact with other copies of
themselves on the battlefield or in another zone.
(Ex: Plague Rats or Accumulated Knowledge.)