Guide of Souls

Whenever another creature you control enters, you gain 1 life and get {E} (an energy counter).
Whenever you attack, you may pay {E}{E}{E}. When you do, put two +1/+1 counters and a flying counter on target attacking creature. It becomes an Angel in addition to its other types.

Case of the Uneaten Feast

Whenever a creature you control enters, you gain 1 life.
To solve — You've gained 5 or more life this turn. (If unsolved, solve at the beginning of your end step.)
Solved — Sacrifice this Case: Creature cards in your graveyard gain "You may cast this card from your graveyard" until end of turn.

Windswept Heath

{T}, Pay 1 life, Sacrifice Windswept Heath: Search your library for a Forest or Plains card, put it onto the battlefield, then shuffle.

Primal Prayers

When Primal Prayers enters, you get {E}{E} (two energy counters).
You may cast creature spells with mana value 3 or less by paying {E} rather than paying their mana costs. If you cast a spell this way, you may cast it as though it had flash.

Cream of the Crop

Whenever a creature you control enters, you may look at the top X cards of your library, where X is that creature's power. If you do, put one of those cards on top of your library and the rest on the bottom of your library in any order.

Champion of Lambholt

Creatures with power less than Champion of Lambholt's power can't block creatures you control.
Whenever another creature you control enters, put a +1/+1 counter on Champion of Lambholt.

Genesis Chamber

Whenever a nontoken creature enters, if Genesis Chamber is untapped, that creature's controller creates a 1/1 colorless Myr artifact creature token.

Whitemane Lion

Flash
When Whitemane Lion enters, return a creature you control to its owner's hand.

Plains

Attended Socialite

Alliance — Whenever another creature you control enters, Attended Socialite gets +1/+1 until end of turn.

Explore

You may play an additional land this turn.
Draw a card.

Lush Portico

({T}: Add {G} or {W}.)
Lush Portico enters tapped.
When Lush Portico enters, surveil 1. (Look at the top card of your library. You may put it into your graveyard.)

Chatterstorm

Create a 1/1 green Squirrel creature token.
Storm (When you cast this spell, copy it for each spell cast before it this turn.)

Decoction Module

Whenever a creature you control enters, you get {E} (an energy counter).
{4}, {T}: Return target creature you control to its owner's hand.

Farseek

Search your library for a Plains, Island, Swamp, or Mountain card, put it onto the battlefield tapped, then shuffle.

Stonecloaker

Flash
Flying
When Stonecloaker enters, return a creature you control to its owner's hand.
When Stonecloaker enters, exile target card from a graveyard.

Forest

Rumor Gatherer

Alliance — Whenever another creature you control enters, scry 1. If this is the second time this ability has resolved this turn, draw a card instead.

Greenbelt Rampager

When Greenbelt Rampager enters, pay {E}{E} (two energy counters). If you can't, return Greenbelt Rampager to its owner's hand and you get {E}.