Sunforger
Artifact — Equipment
Equipped creature gets +4/+0.
, Unattach this Equipment: Search your library for a red or white instant card with mana value 4 or less and cast that card without paying its mana cost. Then shuffle.
Equip
Darrell Riche
Rulings
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 card has any mandatory additional costs, those must be paid to cast the spell.
(wotc • 2020-08-07)
You can't pay the cost of unattaching Sunforger unless Sunforger is attached to a creature.
(wotc • 2020-08-07)
If a spell has {X} in its mana cost, you must choose 0 as the value of X when casting it without paying its mana cost.
(wotc • 2020-08-07)
Rulings
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 card has any mandatory additional costs, those must be paid to cast the spell.
(wotc • 2020-08-07)
You can't pay the cost of unattaching Sunforger unless Sunforger is attached to a creature.
(wotc • 2020-08-07)
If a spell has {X} in its mana cost, you must choose 0 as the value of X when casting it without paying its mana cost.
(wotc • 2020-08-07)