Cheapest priced copy (Magic Origins): $0.35 at Card Kingdom, near mint, their price list as of .
Deep-Sea Terror 
Creature — Serpent · 6/6 · Common · Magic Origins · #52
This creature can't attack unless there are seven or more cards in your graveyard.
Legal inCommanderPioneerModernLegacyVintagePauper
Not legal inBrawlStandard
1 printing · $0.35 to $0.49 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Magic Origins | 52 | Common | $0.35 | $0.49 |
One ruling from Wizards of the Coast
- 22 June 2015Deep-Sea Terror’s ability only checks as attackers are declared. After Deep-Sea Terror legally attacks, reducing the number of cards in your graveyard won’t cause it to stop attacking.