Surtland Elementalist
Creature — Giant Wizard
As an additional cost to cast this spell, reveal a Giant card from your hand or pay 
.
Whenever this creature attacks, you may cast an instant or sorcery spell from your hand without paying its mana cost.
Nicholas Gregory
Kaldheim (KHM)
• #375Rulings
If you cast a spell using Surtland Elementalist’s triggered ability, you do so as part of the resolution of that ability. You can’t wait to cast the spell later in the turn. Timing permissions based on the card’s type are ignored, and the spell will resolve before blockers are declared.
(wotc • 2021-02-05)
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, such as kicker costs. If the card has any mandatory additional costs, those must be paid to cast the spell.
(wotc • 2021-02-05)
A Giant card is a creature card with the creature type Giant. Presumably, it will be the same size as all your other cards.
(wotc • 2021-02-05)
If the spell has {X} in its mana cost, you must choose 0 as the value of X.
(wotc • 2021-02-05)
Rulings
If you cast a spell using Surtland Elementalist’s triggered ability, you do so as part of the resolution of that ability. You can’t wait to cast the spell later in the turn. Timing permissions based on the card’s type are ignored, and the spell will resolve before blockers are declared.
(wotc • 2021-02-05)
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, such as kicker costs. If the card has any mandatory additional costs, those must be paid to cast the spell.
(wotc • 2021-02-05)
A Giant card is a creature card with the creature type Giant. Presumably, it will be the same size as all your other cards.
(wotc • 2021-02-05)
If the spell has {X} in its mana cost, you must choose 0 as the value of X.
(wotc • 2021-02-05)