Cheapest priced copy (Adventures in the Forgotten Realms): $0.49 at Card Kingdom, near mint, their price list as of .
Dragon Turtle 
Creature — Dragon Turtle · 3/5 · Rare · Adventures in the Forgotten Realms · #56
Flash
Drag Below — When this creature enters, tap it and up to one target creature an opponent controls. They don't untap during their controllers' next untap steps.
Legal inCommanderPioneerModernLegacyVintage
Not legal inBrawlStandardPauper
5 printings · $0.49 to $12.99 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Adventures in the Forgotten Realms | 56 | Rare | $0.49 | $0.49 |
| Adventures in the Forgotten Realms | 307 | Rare | $0.49 | $0.49 |
| Adventures in the Forgotten Realms Promos | 56a | Rare | — | $12.99 |
| Adventures in the Forgotten Realms Promos | 56p | Rare | $0.49 | $0.79 |
| Adventures in the Forgotten Realms Promos | 56s | Rare | — | $1.29 |
2 rulings from Wizards of the Coast
- 23 July 2021If you target an opponent's creature with Dragon Turtle's Drag Below ability and that target is illegal as the ability tries to resolve, the entire ability is removed from the stack and does nothing. Dragon Turtle will remain untapped and will untap as normal during its controller's next untap step.
- 23 July 2021If, however, there are no legal targets for the Drag Below ability when Dragon Turtle enters the battlefield (or you choose not to target anything), Dragon Turtle's ability will still resolve and cause it to be tapped and it won't untap during its controllers next untap step.