The first wave of collector booster boxes had a collection of premium Sol Rings available in both serialized and non-serialized quantities
"Witch's Prophecy" skinned Force of Negation)
Things like Kokusho, the Evening Star and Yawgmoth, Thran Physician are must-plays in any deck I have with black, and considering Gray Merchant of Asphodel might also be worth your time
The latter scenario, known as decking out, transpires when a player is unable to draw a card when required, adding an additional layer of strategic depth to the game.
Another Final Fantasy IX alumni, Beatrix is clearly intended as a glue card to bring all the Equipment synergies in the deck together
Specifically, whenever an effect asks you to draw a card and your library is empty, you lose the next time a player would receive priority (which, in practice, pretty much means on the spot , regardless of what's in play or on the stack)