Ominous Sphinx

Creature — Sphinx

Produces: nothing.

Cares about: anything being discarded.

Partners

95 cards can cause a Sphinx creature or artifact or enchantment or planeswalker or instant or sorcery or battle it makes cheaper to cast.

1. Unesh, Criosphinx Sovereign — Unesh, Criosphinx Sovereign reduces what Ominous Sphinx costs

1,609 cards can cause anything being discarded.

1. Transplant Theorist — When Transplant Theorist discards a card, Ominous Sphinx shrinks a creature by -2/-0
2. Leonardo da Vinci — When Leonardo da Vinci discards a card, Ominous Sphinx shrinks a creature by -2/-0
3. Kiora, the Rising Tide — When Kiora, the Rising Tide discards a card, Ominous Sphinx shrinks a creature by -2/-0
4. Cephalid Coliseum — When Cephalid Coliseum discards a card, Ominous Sphinx shrinks a creature by -2/-0
5. Conqueror's Galleon // Conqueror's Foothold — When Conqueror's Galleon // Conqueror's Foothold discards a card, Ominous Sphinx shrinks a creature by -2/-0
6. Sidequest: Card Collection // Magicked Card — When Sidequest: Card Collection // Magicked Card discards a card, Ominous Sphinx shrinks a creature by -2/-0
7. Gran-Gran — When Gran-Gran discards a card, Ominous Sphinx shrinks a creature by -2/-0
8. Cephalid Sage — When Cephalid Sage discards a card, Ominous Sphinx shrinks a creature by -2/-0

366 other cards cause it too, equally specific. The ones shown are the best connected.