Cheapest priced copy (Ravnica Allegiance): $0.35 at Card Kingdom, near mint, their price list as of .
Tower Defense 
Instant · Uncommon · Ravnica Allegiance · #147
Creatures you control get +0/+5 and gain reach until end of turn.
Legal inCommanderPioneerModernLegacyVintage
Not legal inBrawlStandardPauper
3 printings · $0.35 to $3.99 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Gatecrash | 137 | Uncommon | $0.39 | $3.99 |
| Ravnica Allegiance | 147 | Uncommon | $0.35 | $2.49 |
| Tarkir: Dragonstorm Commander | 275 | Uncommon | $0.35 | — |
One ruling from Wizards of the Coast
- 24 January 2013Only creatures you control when Tower Defense resolves will get the bonuses. Creatures that come under your control later that turn will not.