Mountain

Shock

Quick Draw

Target creature you control gets +1/+1 and gains first strike until end of turn. Creatures target opponent controls lose first strike and double strike until end of turn.

Blackcleave Cliffs

Blackcleave Cliffs enters tapped unless you control two or fewer other lands.
{T}: Add {B} or {R}.

Might of the Meek

Target creature gains trample until end of turn. It also gets +1/+0 until end of turn if you control a Mouse.
Draw a card.

Outlaws' Fury

Creatures you control get +2/+0 until end of turn. If you control an outlaw, exile the top card of your library. Until the end of your next turn, you may play that card. (Assassins, Mercenaries, Pirates, Rogues, and Warlocks are outlaws.)

Skulduggery

Until end of turn, target creature you control gets +1/+1 and target creature an opponent controls gets -1/-1.

Blazing Crescendo

Target creature gets +3/+1 until end of turn.
Exile the top card of your library. Until the end of your next turn, you may play that card.

Jagged Barrens

Jagged Barrens enters tapped.
When Jagged Barrens enters, it deals 1 damage to target opponent.
{T}: Add {B} or {R}.

Swamp

Shoot the Sheriff

Destroy target non-outlaw creature. (Assassins, Mercenaries, Pirates, Rogues, and Warlocks are outlaws. Everyone else is fair game.)

Fake Your Own Death

Until end of turn, target creature gets +2/+0 and gains "When this creature dies, return it to the battlefield tapped under its owner's control and you create a Treasure token." (It's an artifact with "{T}, Sacrifice this token: Add one mana of any color.")

Cacophony Scamp

Whenever Cacophony Scamp deals combat damage to a player, you may sacrifice it. If you do, proliferate. (Choose any number of permanents and/or players, then give each another counter of each kind already there.)
When Cacophony Scamp dies, it deals damage equal to its power to any target.