Cheapest priced copy (Modern Masters 2015): $0.49 at Card Kingdom, near mint, their price list as of .
Chimeric Mass 
Artifact · Rare · Scars of Mirrodin · #141
This artifact enters with X charge counters on it.
{1}: Until end of turn, this artifact becomes a Construct artifact creature with "This creature's power and toughness are each equal to the number of charge counters on it."
Legal inCommanderModernLegacyVintage
Not legal inBrawlStandardPioneerPauper
2 printings · $0.49 to $1.99 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Modern Masters 2015 | 204 | Rare | $0.49 | $0.99 |
| Scars of Mirrodin | 141 | Rare | $0.49 | $1.99 |
4 rulings from Wizards of the Coast
- 1 January 2011If you activate Chimeric Mass’s last ability while it has no charge counters on it, it will become a 0/0 creature and be put into its owner’s graveyard as a state-based action.
- 1 January 2011Activating the last ability while Chimeric Mass is a creature will override any effects that set its power and/or toughness to another number, but effects that modify power and/or toughness without directly setting them will still apply.
- 1 January 2011If the number of charge counters on Chimeric Mass changes while it is a creature, its power and toughness will change accordingly.
- 1 January 2011For example, say you activate the last ability of a Chimeric Mass with three charge counters on it. After it resolves, you cast Giant Growth targeting it. It’s now 6/6. Then Diminish (“Target creature becomes 1/1 until end of turn”) is cast targeting it. Once Diminish resolves, Chimeric Mass would be 4/4. Activating Chimeric Mass’s last ability a second time would make it 6/6 again until end of turn.