Gray Merchant of Asphodel

When Gray Merchant of Asphodel enters, each opponent loses X life, where X is your devotion to black. You gain life equal to the life lost this way. (Each {B} in the mana costs of permanents you control counts toward your devotion to black.)

Acidic Slime

Deathtouch (Any amount of damage this deals to a creature is enough to destroy it.)
When Acidic Slime enters, destroy target artifact, enchantment, or land.

Gladecover Scout

Hexproof (This creature can't be the target of spells or abilities your opponents control.)

Golgari Guildgate

This land enters tapped.
{T}: Add {B} or {G}.

Colossal Heroics

Strive — This spell costs {1}{G} more to cast for each target beyond the first.
Any number of target creatures each get +2/+2 until end of turn. Untap those creatures.

Viridian Emissary

When Viridian Emissary dies, you may search your library for a basic land card, put it onto the battlefield tapped, then shuffle.

Dryad Sophisticate

Nonbasic landwalk (This creature can't be blocked as long as defending player controls a nonbasic land.)

Torrent Elemental

Flying
Whenever Torrent Elemental attacks, tap all creatures defending player controls.
{3}{B/G}{B/G}: Put Torrent Elemental from exile onto the battlefield tapped. Activate only as a sorcery.

Nylea's Presence

Enchant land
When Nylea's Presence enters, draw a card.
Enchanted land is every basic land type in addition to its other types.

Mirror Match

Cast this spell only during the declare blockers step.
For each creature attacking you or a planeswalker you control, create a token that's a copy of that creature and that's blocking that creature. Exile those tokens at end of combat.

Mulldrifter

Flying
When Mulldrifter enters, draw two cards.
Evoke {2}{U} (You may cast this spell for its evoke cost. If you do, it's sacrificed when it enters.)