Mountain

Goblin Oriflamme

Attacking creatures you control get +1/+0.

Tattermunge Maniac

Tattermunge Maniac attacks each combat if able.

Experiment One

Evolve (Whenever a creature you control enters, if that creature has greater power or toughness than this creature, put a +1/+1 counter on this creature.)
Remove two +1/+1 counters from Experiment One: Regenerate Experiment One. (The next time this creature would be destroyed this turn, instead tap it, remove it from combat, and heal all damage on it.)

Rakdos Cackler

Unleash (You may have this creature enter with a +1/+1 counter on it. It can't block as long as it has a +1/+1 counter on it.)

Zurgo Bellstriker

Zurgo Bellstriker can't block creatures with power 2 or greater.
Dash {1}{R} (You may cast this spell for its dash cost. If you do, it gains haste, and it's returned from the battlefield to its owner's hand at the beginning of the next end step.)

Rigging Runner

First strike
Raid — Rigging Runner enters with a +1/+1 counter on it if you attacked this turn.

Furnace Scamp

Whenever Furnace Scamp deals combat damage to a player, you may sacrifice it. If you do, Furnace Scamp deals 3 damage to that player.

Uktabi Drake

Flying, haste
Echo {1}{G}{G} (At the beginning of your upkeep, if this came under your control since the beginning of your last upkeep, sacrifice it unless you pay its echo cost.)

Forest

Old-Growth Dryads

When Old-Growth Dryads enters, each opponent may search their library for a basic land card, put it onto the battlefield tapped, then shuffle.

Rogue Elephant

When Rogue Elephant enters, sacrifice it unless you sacrifice a Forest.

Scythe Tiger

Shroud (This creature can't be the target of spells or abilities.)
When Scythe Tiger enters, sacrifice it unless you sacrifice a land.