Cheapest priced copy (Prophecy): $0.79 at Card Kingdom, near mint, their price list as of .
Dual Nature 
Enchantment · Rare · Prophecy · #112
Whenever a nontoken creature enters, its controller creates a token that's a copy of that creature.
Whenever a nontoken creature leaves the battlefield, exile all tokens with the same name as that creature.
When this enchantment leaves the battlefield, exile all tokens created with this enchantment.
Legal inCommanderLegacyVintage
Not legal inBrawlStandardPioneerModernPauper
1 printing · $0.79 to $15.99 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Prophecy | 112 | Rare | $0.79 | $15.99 |
4 rulings from Wizards of the Coast
- 4 October 2004If Dual Nature leaves the battlefield between when it triggers and when a token is put onto the battlefield, that token remains on the battlefield indefinitely. It missed the separate ability which would have exiled the token.
- 4 October 2004If the original creature has any "enters" abilities, the copy will also have those.
- 1 October 2009The token is not considered to have been kicked, even if the creature it's a copy of was kicked.
- 1 July 2013If a legendary creature enters the battlefield, the token is put onto the battlefield and then the "legend rule" forces its controller to put either the original or the token into its owner's graveyard before any player can take any actions.