Cheapest priced copy (Dissension): $5.99 at Card Kingdom, near mint, their price list as of .
Omnibian 
Creature — Frog · 3/3 · Rare · Dissension · #119
{T}: Target creature becomes a Frog with base power and toughness 3/3 until end of turn.
Legal inCommanderModernLegacyVintage
Not legal inBrawlStandardPioneerPauper
2 printings · $5.99 to $12.99 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Dissension | 119 | Rare | $5.99 | $12.99 |
| RNA Guild Kit | 121 | Rare | $6.49 | — |
3 rulings from Wizards of the Coast
- 1 May 2006If the target creature has any counters on it that modify its power and toughness (such as a +1/+1 counter), those counters will continue to affect the creature after it becomes 3/3. In the example given, it will be 4/4.
- 1 October 2009If the target creature is affected by any effects that modify its power or toughness without setting them to specific values (such as from Giant Growth), Omnibian’s effect will be applied before those effects. In the example given, the creature will be 6/6.
- 15 April 2013This effect changes only the power, toughness, and creature type of the targeted creature. It does not cause that creature to lose any abilities.