Cheapest priced copy (Eventide): $0.35 at Card Kingdom, near mint, their price list as of .
Unnerving Assault 
Instant · Uncommon · Eventide · #114
Creatures your opponents control get -1/-0 until end of turn if {U} was spent to cast this spell, and creatures you control get +1/+0 until end of turn if {R} was spent to cast this spell. (Do both if {U}{R} was spent.)
Legal inCommanderModernLegacyVintage
Not legal inBrawlStandardPioneerPauper
1 printing · $0.35 to $0.49 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Eventide | 114 | Uncommon | $0.35 | $0.49 |
5 rulings from Wizards of the Coast
- 1 August 2008Unnerving Assault affects only creatures on the battlefield at the time it resolves. If a creature enters later that turn, it won't be affected.
- 1 August 2008The spell cares about what mana was spent to pay its total cost, not just what mana was spent to pay the hybrid part of its cost.
- 1 August 2008If a creature changes controllers later in the turn, that won't change how Unnerving Assault affected it.
- 1 August 2008If the spell is copied, the copy will never have had mana of the stated color paid for it, no matter what colors were spent on the original spell.
- 1 August 2008The spell checks on resolution to see if any mana of the stated colors was spent to pay its cost. If so, it doesn't matter how much mana of that color was spent.