Cheapest priced copy (Mirage): $4.99 at Card Kingdom, near mint, their price list as of .
Delirium 
Instant · Uncommon · Mirage · #260
Cast this spell only during an opponent's turn.
Tap target creature that player controls. That creature deals damage equal to its power to the player. Prevent all combat damage that would be dealt to and dealt by the creature this turn.
Legal inCommanderLegacyVintage
Not legal inBrawlStandardPioneerModernPauper
1 printing · $4.99 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Mirage | 260 | Uncommon | $4.99 | — |
One ruling from Wizards of the Coast
- 4 October 2004Tapping the creature is part of the effect and not the cost, therefore you can cast this targeting a tapped creature.