in its mana cost, you must choose 0 as the value of X when casting it without paying its mana cost.Buster Sword turns a successful combat hit into both a card and a potential free spell. The equipped creature receives +3/+2, and when it deals combat damage to a player, you draw a card and may cast a spell from your hand with mana value no greater than the damage dealt. That connects combat power directly to the size of the spell you can deploy.
Evasive creatures are strong carriers because the payoff requires damage to a player. Flyers, unblockable creatures, and attackers with trample can make the trigger more reliable, while double strike can create separate opportunities if the creature deals combat damage in both damage steps. Equipment-focused decks can use Stoneforge Mystic to find the Sword or Sigarda's Aid to attach it as it enters.
The trigger draws before offering the cast, so the newly drawn card can be a candidate if it meets the mana-value requirement. The permission allows the spell to be cast during the trigger's resolution, but you still need to follow restrictions and pay any required additional costs. A spell with X in its mana cost normally requires X to be zero when cast without paying that cost.
Choose a carrier that can connect consistently rather than one with high power alone. The Sword costs three mana to cast and two to equip, so protecting that investment matters. Its best turns combine a meaningful attack with a free spell that develops your board or answers an opposing threat immediately.
