Cheapest priced copy (Commander 2013): $0.35 at Card Kingdom, near mint, their price list as of .
Azorius Herald 
Creature — Spirit · 2/1 · Uncommon · Dissension · #2
This creature can't be blocked.
When this creature enters, you gain 4 life.
When this creature enters, sacrifice it unless {U} was spent to cast it.
Legal inCommanderModernLegacyVintage
Not legal inBrawlStandardPioneerPauper
4 printings · $0.35 to $0.49 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Commander 2013 | 6 | Uncommon | $0.35 | — |
| Dissension | 2 | Uncommon | $0.35 | $0.49 |
| RNA Guild Kit | 2 | Uncommon | $0.35 | — |
| The List | GK2-2 | 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.