Cheapest priced copy (New Phyrexia): $0.35 at Card Kingdom, near mint, their price list as of .
Viridian Betrayers 
Creature — Phyrexian Elf Warrior · 3/1 · Common · New Phyrexia · #124
This creature has infect as long as an opponent is poisoned. (It deals damage to creatures in the form of -1/-1 counters and to players in the form of poison counters.)
Legal inCommanderModernLegacyVintagePauper
Not legal inBrawlStandardPioneer
1 printing · $0.35 to $0.99 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| New Phyrexia | 124 | Common | $0.35 | $0.99 |
2 rulings from Wizards of the Coast
- 1 June 2011The player must be poisoned when Viridian Betrayers deals damage in order for Viridian Betrayers to have infect. If the player has no poison counters, damage dealt to that player by Viridian Betrayers will result in loss of life, even if it's dealt at the same time as damage from another creature with infect.
- 1 June 2011A player is poisoned if that player has one or more poison counters.