Cheapest priced copy (Adventures in the Forgotten Realms): $0.69 at Card Kingdom, near mint, their price list as of .
Mind Flayer 
Creature — Horror · 3/3 · Rare · Adventures in the Forgotten Realms · #308
Dominate Monster — When this creature enters, gain control of target creature for as long as you control this creature.
Legal inCommanderPioneerModernLegacyVintage
Not legal inBrawlStandardPauper
6 printings · $0.69 to $8.49 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Adventures in the Forgotten Realms | 63 | Rare | $0.69 | $0.99 |
| Adventures in the Forgotten Realms | 308 | Rare | $0.69 | $0.99 |
| Commander Legends: Battle for Baldur's Gate | 728 | Rare | $0.79 | — |
| Adventures in the Forgotten Realms Promos | 63a | Rare | — | $8.49 |
| Adventures in the Forgotten Realms Promos | 63p | Rare | $1.99 | $2.49 |
| Adventures in the Forgotten Realms Promos | 63s | Rare | — | $2.29 |
One ruling from Wizards of the Coast
- 23 July 2021If Mind Flayer leaves the battlefield or you lose control of it before its Dominate Monster ability resolves, control of the target creature doesn't change at all.