Will

A card's Will has two functions:

• when the card is summoned, collect mana equivalent to this value onto the card;
• if the card is set, before it has been summoned; you can sac it face-down through the Hidden Sacrifice mechanic in order to pay for mana costs.

You can never get both benefits from a single card. Either it is sac'd (or destroyed) face-down, or it is eventually summoned.