From 1994 to 1995, the short lived publishing studio HarperPrism published 5 promotional Magic: The Gathering books
(It won't untap during your next untap step.) Whenever you exert a creature, reveal cards from the top of your library until you reveal an Equipment card
A 4/4 creature for 5 is a reasonable rate as well, though as with most of blacks best mana doublers, being a creature is a pretty significant drawback with the amount of spot removal and board wipes flying around
A straightforward way to use this is by tutoring High Tide, doubling your mana on the next turn
If you knock out your opponents Pokemon, you may claim one Prize card
While Landfall effects vary greatly, all Landfall abilities trigger whenever a land enters the battlefield under its owner's control, allowing for a given effect to be utilized several times within a game