Cheapest priced copy (Darksteel): $0.35 at Card Kingdom, near mint, their price list as of .
Myr Moonvessel 
Artifact Creature — Myr · 1/1 · Common · Darksteel · #133
When this creature dies, add {C}.
Legal inCommanderModernLegacyVintagePauper
Not legal inBrawlStandardPioneer
1 printing · $0.35 to $5.99 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Darksteel | 133 | Common | $0.35 | $5.99 |
2 rulings from Wizards of the Coast
- 25 January 2011The triggered ability isn't a mana ability. It uses the stack and can be responded to.
- 25 January 2011You get the mana whether you want it or not. If you don't spend it, it will disappear at the end of the current step (or phase).