0036: Casting without paying the mana cost

Status: Accepted. Settles the question left open by decision 0031.

Context

Cascade, suspend, discover, and many other effects let a player cast a spell without paying its mana cost. The format had no encoding for this, and spec section 15 listed it as not yet covered. It matters in Modern: Living End and Crashing Footfalls decks are built on cascade and suspend, and a resolved free spell is often the turn that decides the game. Trinisphere is played against them because it makes a free spell cost {3}, which the record needs to explain.

Three things needed a definition: how the free cast itself is written, how the record says what allowed it, and how cascade's random bottom-of-library order is written.

Decision

1. A free cast is the alternative cost choose cost "without paying its mana cost". It is written like any other cost choice, after the cast line. The value is fixed, so there is one way to write it.
2. A card cast while another spell or ability is resolving has that spell or ability as the cast line's cause: #54 "Living End" cast from exile by #51. A card cast as a player's own action, the usual case, still has no cause, including casts allowed by the card's own ability, such as flashback or casting a plotted card.
3. For cost lines, a free cast's first OLD is {0}, including for a card with no mana cost. Cost increases then apply as usual: Trinisphere writes cost {0} -> {3}.
4. Cards put on the bottom of a library together in a random order are written as move ... -> library bottom lines whose order is not their order in the library. Their positions among those cards are unknown, so keyframes give them no position.

Rules basis

Checked against the Comprehensive Rules effective 2026-09-25.

• 118.9: "An alternative cost is a cost listed in a spell's text, or applied to it from another effect, that its controller may pay rather than paying the spell's mana cost. Alternative costs are usually phrased, 'You may [action] rather than pay [this object's] mana cost,' or 'You may cast [this object] without paying its mana cost.'"
• 118.9d: "If an alternative cost is being paid to cast a spell, any additional costs, cost increases, and cost reductions that affect that spell are applied to that alternative cost."
• 118.6, 118.6a: "Some objects have no mana cost. This represents an unpayable cost." and "If an alternative cost is applied to an unpayable cost, including an effect that allows a player to cast a spell without paying its mana cost, the alternative cost may be paid." Living End can be cast this way.
• 117.2e: "Resolving spells and abilities may instruct players to make choices or take actions". Casting a spell during a resolution is such an action, so it has a cause.
• 702.85a: cascade: "You may cast that card without paying its mana cost if the resulting spell's mana value is less than this spell's mana value. Then put all cards exiled this way that weren't cast on the bottom of your library in a random order."
• 702.62a, 702.62d: suspend's last trigger: "you may play it without paying its mana cost if able", and "Casting a spell as an effect of its suspend ability follows the rules for paying alternative costs in rules 601.2b and 601.2f–h."

Alternatives rejected

• A free keyword on the cast line. Rejected: the rules treat a free cast as an alternative cost, and the format already records alternative costs as choose cost. A keyword would be a second way to say the same thing.
• No cause on cast, with the permission implied by the preceding trigger. Rejected: a reader would have to know what cascade does to connect the two, which is the gap the format exists to close.
• Writing randomly ordered bottom cards without bottom. Rejected: they are known to be at the bottom; only their order among themselves is unknown.

Consequences

• Spec sections 7.1, 7.2, and 7.6 define the cast cause, the cost value, the {0} starting cost, and random bottom order. Section 15 no longer lists free casts, and the open question is no longer listed.
• examples/more-situations.md shows Violent Outburst cascading into Living End under Trinisphere.