Cheapest priced copy (Duel Decks: Jace vs. Chandra): $0.35 at Card Kingdom, near mint, their price list as of .
Ophidian 
Creature — Snake · 1/3 · Common · World Championship Decks 1997 · #pm45
Whenever this creature attacks and isn't blocked, you may draw a card. If you do, this creature assigns no combat damage this turn.
Legal inCommanderLegacyVintagePauper
Not legal inBrawlStandardPioneerModern
6 printings · $0.35 to $9.99 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Duel Decks: Jace vs. Chandra | 9 | Common | $0.35 | — |
| Friday Night Magic 2001 | 7 | Rare | — | $9.99 |
| Duel Decks Anthology: Jace vs. Chandra | 9 | Common | $0.35 | — |
| The List | WTH-45 | Common | $0.35 | — |
| World Championship Decks 1997 | pm45 | Common | $0.35 | — |
| Weatherlight | 45 | Common | $0.35 | — |
One ruling from Wizards of the Coast
- 15 April 2013An ability that triggers when something “attacks and isn’t blocked” triggers in the declare blockers step after blockers are declared if (1) that creature is attacking and (2) no creatures are declared to block it. It will trigger even if that creature was put onto the battlefield attacking rather than having been declared as an attacker in the declare attackers step.