Cheapest priced copy (The List): $8.99 at Card Kingdom, near mint, their price list as of .
Whir of Invention 
Instant · Rare · Aether Revolt Promos · #49p
Improvise (Your artifacts can help cast this spell. Each artifact you tap after you're done activating mana abilities pays for {1}.)
Search your library for an artifact card with mana value X or less, put it onto the battlefield, then shuffle.
Legal inCommanderPioneerModernLegacyVintage
Not legal inBrawlStandardPauper
7 printings · $8.99 to $139.99 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Aether Revolt | 49 | Rare | $9.49 | $16.99 |
| Aether Revolt Promos | 49p | Rare | $10.99 | $22.99 |
| Aether Revolt Promos | 49s | Rare | — | $17.99 |
| The List | AER-49 | Rare | $8.99 | — |
| Secret Lair Drop | 311 | Rare | $10.99 | $12.99 |
| Special Guests | 86 | Mythic | $15.99 | $22.99 |
| Special Guests | 96 | Mythic | — | $139.99Out of stock |
9 rulings from Wizards of the Coast
- 9 February 2017Because improvise isn't an alternative cost, it can be used in conjunction with alternative costs.
- 9 February 2017If an artifact you control has a mana ability with {T} in the cost, activating that ability while casting a spell with improvise will result in the artifact being tapped when you pay the spell's costs. You won't be able to tap it again for improvise. Similarly, if you sacrifice an artifact to activate a mana ability while casting a spell with improvise, that artifact won't be on the battlefield when you pay the spell's costs, so you won't be able to tap it for improvise.
- 9 February 2017Tapping an artifact won't cause its abilities to stop applying unless those abilities say so.
- 9 February 2017Improvise can't be used to pay for anything other than the cost of casting the spell. For example, it can't be used during the resolution of an ability that says "Counter target spell unless its controller pays {3}."
- 9 February 2017Improvise can't pay for {W}, {U}, {B}, {R}, {G}, or {C} mana symbols in a spell's total cost.
- 9 February 2017When calculating a spell's total cost, include any alternative costs, additional costs, or anything else that increases or reduces the cost to cast the spell. Improvise applies after the total cost is calculated.
- 9 February 2017Equipment attached to a creature doesn't become tapped when that creature becomes tapped, and tapping that Equipment doesn't cause the creature to become tapped.
- 9 February 2017When using improvise to cast a spell with {X} in its mana cost, first choose the value for X. That choice, plus any cost increases or decreases, will determine the spell's total cost. Then you can tap artifacts you control to help pay that cost. For example, if you cast Whir of Invention (a spell with improvise and mana cost {X}{U}{U}{U}) and choose X to be 3, the total cost is {3}{U}{U}{U}. If you tap two artifacts, you'll have to pay {1}{U}{U}{U}.
- 9 February 2017Improvise doesn't change a spell's mana cost or mana value.