As Seal of the Guildpact enters the battlefield, choose two colors.
Each spell you cast costsless to cast for each of the chosen colors it is.
11/4/2015 You must choose two different colors.
11/4/2015 Seal of the Guildpact’s last ability doesn’t change the mana cost or converted mana cost of any spell. It changes only the total cost you pay.
11/4/2015 Seal of the Guildpact’s last ability can’t reduce the amount of colored mana you pay for a spell. It reduces only the generic component of that cost.
11/4/2015 If there are additional costs to cast a spell, or if the cost to cast a spell is increased by an effect (such as the one created by Thalia, Guardian of Thraben’s ability), apply those increases before applying cost reductions.
11/4/2015 The cost reduction can apply to alternative costs such as evoke costs.
11/4/2015 If a spell you cast has in its mana cost, you choose the value of X before calculating the spell’s total cost. For example, if that spell’s mana cost is and you’ve chosen red and green, you could choose 5 as the value of X and pay to cast the spell.