Madness: A Discard With a Detour
Judge Level 2Fiery Temper leaves your hand — and lands on the stack as 3 damage.
Cards involved
The discard
You cast Lightning Axe (additional cost: discard a card) and discard Fiery Temper — a card with madness 
.
702.35aMadness is a keyword that represents two abilities. The first is a static ability that functions while the card with madness is in a player’s hand. The second is a triggered ability that functions when the first ability is applied. “Madness [cost]” means “If a player would discard this card, that player discards it, but exiles it instead of putting it into their graveyard” and “When this card is exiled this way, its owner may cast it by paying [cost] rather than paying its mana cost. If that player doesn’t, they put this card into their graveyard.”
Madness steps in
The discard replacement sends Fiery Temper to EXILE instead of the graveyard, and a triggered ability goes on the stack — above the Axe.
702.35aMadness is a keyword that represents two abilities. The first is a static ability that functions while the card with madness is in a player’s hand. The second is a triggered ability that functions when the first ability is applied. “Madness [cost]” means “If a player would discard this card, that player discards it, but exiles it instead of putting it into their graveyard” and “When this card is exiled this way, its owner may cast it by paying [cost] rather than paying its mana cost. If that player doesn’t, they put this card into their graveyard.”
What happens?
The trigger is about to resolve.
What does Fiery Temper cost you — and how do you cast it?
Pick an answer to continue.
One-two punch
You cast Fiery Temper for (3 damage), with the Axe (5 damage) still waiting below. If you decline the cast, Fiery Temper goes to the graveyard only then (702.35a). Rule of thumb: madness = replacement + trigger + normal cast — three building blocks to know separately.
Stack
Lightning Axe
Additional cost: discard a card; 5 damage to a creature
Fiery Temper
, madness : 3 damage to any target
Triggered ability: Fiery Temper
Madness trigger: cast from exile for ?
The stack is empty.
In short
How does madness work when you discard a card like Fiery Temper?
Show answer Hide answer
Madness is a chain (702.35): the static part replaces the discard with exile, the triggered part asks on resolution: cast it for the madness cost? The cast itself is an entirely normal cast with an alternative cost (702.35b) — counterable and all.
702.35aMadness is a keyword that represents two abilities. The first is a static ability that functions while the card with madness is in a player’s hand. The second is a triggered ability that functions when the first ability is applied. “Madness [cost]” means “If a player would discard this card, that player discards it, but exiles it instead of putting it into their graveyard” and “When this card is exiled this way, its owner may cast it by paying [cost] rather than paying its mana cost. If that player doesn’t, they put this card into their graveyard.”
702.35bCasting a spell using its madness ability follows the rules for paying alternative costs in rules 601.2b and 601.2f–h.
702.35cAfter resolving a madness triggered ability, if the exiled card wasn’t cast and was moved to a public zone, effects referencing the discarded card can find that card. See rule 400.7k.