Conspiracy is a special Enchantment card from Time Spiral Timeshifted (TSB), collector number 39. Current market price: $2.58 (foil $6.00), TCGplayer market prices via Scryfall.
As this enchantment enters, choose a creature type. Creatures you control are the chosen type. The same is true for creature spells you control and creature cards you own that aren't on the battlefield.