If you cast a spell "without paying its mana cost," you can't choose to cast it for any alternative costs. You can, however, pay additional costs. If the spell has any mandatory additional costs, you must pay those to cast the spell.
2026-03-20
You cast the spell while Herald of Amity's second ability is resolving and still on the stack. You can't wait to cast it later in the turn. Timing restrictions based on the card's types are ignored.
2026-03-20
If the exiled Aura has in its mana cost, you must choose 0 as the value of X when casting it without paying its mana cost.
2026-03-20
The value of X is calculated at the time Herald of Amity's last ability resolves.
Flying
When this creature enters, exile the top eight cards of your library. You may cast an Aura spell from among them without paying its mana cost. Then put the rest on the bottom of your library in a random order.
Whenever this creature attacks, it gets +X/+X until end of turn, where X is the number of Auras you control.
in its mana cost, you must choose 0 as the value of X when casting it without paying its mana cost.