From Archon Arcana - The KeyForge Wiki
Reference cards are included in KeyForge Archon decks to convey helpful information to players. These cards should be kept near the play area, where either player can view them. Reference cards never enter play and are not controlled by either player.
Examples of reference cards include the Archon Identity card, the Tide reference, Token Creature references, and Quick Reference cards.
—KeyForge Master Rulebook v17 April 2023