Cheapest priced copy (Commander 2015): $0.35 at Card Kingdom, near mint, their price list as of .
Patagia Viper 
Creature — Snake · 2/1 · Uncommon · Dissension · #89
Flying
When this creature enters, create two 1/1 green and blue Snake creature tokens.
When this creature enters, sacrifice it unless {U} was spent to cast it.
Legal inCommanderModernLegacyVintage
Not legal inBrawlStandardPioneerPauper
3 printings · $0.35 to $0.79 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Commander 2015 | 197 | Uncommon | $0.35 | — |
| Dissension | 89 | Uncommon | $0.35 | $0.79 |
| The List | DIS-89 | Uncommon | $0.35 | — |
One ruling from Wizards of the Coast
- 1 May 2006If this enters in a way other than announcing it as a spell, then the appropriate mana can't have been paid, and you'll have to sacrifice it.