Void-Crafting

As an additional cost to cast Void-Crafting, sacrifice X lands.
Create an X/X colourless Eldrazi creature token.
Create X 1/1 colourless Eldrazi Scion creature tokens with 'sacrifice this creature: Add {c}'.
Reveal the top card of your library. If its converted mana cost is X or less, cast it without paying its mana cost.