Frilled Mystic

Flash
When Frilled Mystic enters the battlefield, you may counter target spell.

Acidic Slime

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

Eternal Witness

When Eternal Witness enters the battlefield, you may return target card from your graveyard to your hand.

Reclamation Sage

When Reclamation Sage enters the battlefield, you may destroy target artifact or enchantment.

Momir Vig, Simic Visionary

Whenever you cast a green creature spell, you may search your library for a creature card, reveal it, then shuffle and put that card on top.
Whenever you cast a blue creature spell, reveal the top card of your library. If it's a creature card, put that card into your hand.

Jungle Barrier

Defender (This creature can't attack.)
When Jungle Barrier enters the battlefield, draw a card.

Sakura-Tribe Elder

Sacrifice Sakura-Tribe Elder: Search your library for a basic land card, put that card onto the battlefield tapped, then shuffle.

Coiling Oracle

When Coiling Oracle enters the battlefield, reveal the top card of your library. If it's a land card, put it onto the battlefield. Otherwise, put that card into your hand.