Cheapest priced copy (March of the Machine Commander): $22.99 at Card Kingdom, near mint, their price list as of .
Uncivil Unrest 
Enchantment · Rare · Secret Lair Drop · #2008
Nontoken creatures you control have riot. (They enter with your choice of a +1/+1 counter or haste.)
If a creature you control with a +1/+1 counter on it would deal damage to a permanent or player, it deals double that damage instead.
Legal inCommanderLegacyVintage
Not legal inBrawlStandardPioneerModernPauper
3 printings · $22.99 to $34.99 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| March of the Machine Commander | 35 | Rare | $22.99 | — |
| March of the Machine Commander | 122 | Rare | $22.99 | — |
| Secret Lair Drop | 2008 | Rare | $22.99 | $34.99 |
5 rulings from Wizards of the Coast
- 14 April 2023The damage is dealt by the same source as the original source of damage. The doubled damage isn’t dealt by Uncivil Unrest unless it was somehow the original source of damage.
- 14 April 2023If damage dealt by a creature you control with a +1/+1 counter on it is being divided or assigned among multiple permanents and/or players, that damage is divided or assigned before doubling. For example, if you attack with a 5/5 creature with trample and it’s blocked by a 2/2 creature, you can assign 2 damage to the blocker and 3 damage to the defending player. Those amounts are then doubled to 4 and 6, respectively.
- 14 April 2023If you choose for the creature to gain haste, it gains haste indefinitely. It won’t lose it as the turn ends or as another player gains control of it.
- 14 April 2023If another effect (or effects) modifies how much damage your creature with a +1/+1 counter on it would deal—by preventing some of it, for example—the player being dealt damage or the controller of the permanent being dealt damage chooses the order in which any such effects (including Uncivil Unrest’s) apply. If all of the damage is prevented, Uncivil Unrest’s effect no longer applies.
- 14 April 2023Riot is a replacement effect. Players can’t respond to your choice of +1/+1 counter or haste, and they can’t take actions while the creature is on the battlefield without one or the other.