Cheapest priced copy (Modern Masters 2017): $0.35 at Card Kingdom, near mint, their price list as of .
Spire Monitor 
Creature — Phyrexian Drake · 3/3 · Common · Modern Masters 2017 · #52
Flash (You may cast this spell any time you could cast an instant.)
Flying
Legal inCommanderModernLegacyVintagePauper
Not legal inBrawlStandardPioneer
3 printings · $0.35 to $0.49 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Modern Masters 2017 | 52 | Common | $0.35 | $0.49 |
| New Phyrexia | 46 | Common | $0.35 | $0.49 |
| The List | MM3-52 | Common | $0.35 | — |