Cheapest priced copy (Dark Ascension): $2.99 at Card Kingdom, near mint, their price list as of .
Beguiler of Wills 
Creature — Human Wizard · 1/1 · Mythic · Dark Ascension · #28
{T}: Gain control of target creature with power less than or equal to the number of creatures you control.
Legal inCommanderModernLegacyVintage
Not legal inBrawlStandardPioneerPauper
1 printing · $2.99 to $11.99 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Dark Ascension | 28 | Mythic | $2.99 | $11.99 |
2 rulings from Wizards of the Coast
- 22 January 2011The control-changing effect lasts indefinitely, even if the power of the creature becomes greater than the number of creatures you control after the ability resolves.
- 22 January 2011In order to activate the ability, you must be able to target a creature with power less than or equal to the number of creatures you control. The comparison is made again when the ability resolves. If the power is greater than the number of creatures you control at that time, the target is illegal and the ability doesn’t resolve.