Waterspout Warden

Whenever Waterspout Warden attacks, if another creature entered the battlefield under your control this turn, Waterspout Warden gains flying until end of turn.

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.)

Thousand-Year Elixir

You may activate abilities of creatures you control as though those creatures had haste.
{1}, {T}: Untap target creature.

Eternal Witness

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

Mistbreath Elder

At the beginning of your upkeep, return another creature you control to its owner's hand. If you do, put a +1/+1 counter on Mistbreath Elder. Otherwise, you may return Mistbreath Elder to its owner's hand.

Clifftop Lookout

Reach
When Clifftop Lookout enters, reveal cards from the top of your library until you reveal a land card. Put that card onto the battlefield tapped and the rest on the bottom of your library in a random order.

Maskwood Nexus

Creatures you control are every creature type. The same is true for creature spells you control and creature cards you own that aren't on the battlefield.
{3}, {T}: Create a 2/2 blue Shapeshifter creature token with changeling. (It is every creature type.)

Poison Dart Frog

Reach
{T}: Add one mana of any color.
{2}: Poison Dart Frog gains deathtouch until end of turn.

Coiling Oracle

When Coiling Oracle enters, 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.

Talisman of Curiosity

{T}: Add {C}.
{T}: Add {G} or {U}. Talisman of Curiosity deals 1 damage to you.

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.

Panharmonicon

If an artifact or creature entering causes a triggered ability of a permanent you control to trigger, that ability triggers an additional time.

Commander's Sphere

{T}: Add one mana of any color in your commander's color identity.
Sacrifice Commander's Sphere: Draw a card.

Spore Frog

Sacrifice Spore Frog: Prevent all combat damage that would be dealt this turn.

Simic Signet

Dreamdew Entrancer

Reach
When Dreamdew Entrancer enters, tap up to one target creature and put three stun counters on it. If you control that creature, draw two cards.

Sunshower Druid

When Sunshower Druid enters, put a +1/+1 counter on target creature and you gain 1 life.

Kindred Discovery

As Kindred Discovery enters, choose a creature type.
Whenever a creature you control of the chosen type enters or attacks, draw a card.

Skyskipper Duo

Flying
When Skyskipper Duo enters, exile up to one other target creature you control. Return it to the battlefield under its owner's control at the beginning of the next end step.

Beast Whisperer

Whenever you cast a creature spell, draw a card.

Bellowing Crier

When Bellowing Crier enters, draw a card, then discard a card.

Reclamation Sage

When this creature enters, you may destroy target artifact or enchantment.

Splash Lasher

Offspring {1}{U} (You may pay an additional {1}{U} as you cast this spell. If you do, when this creature enters, create a 1/1 token copy of it.)
When this creature enters, tap up to one target creature and put a stun counter on it. (If a permanent with a stun counter would become untapped, remove one from it instead.)

Pond Prophet

Plaxcaster Frogling

Graft 3 (This creature enters with three +1/+1 counters on it. Whenever another creature enters, you may move a +1/+1 counter from this creature onto it.)
{2}: Target creature with a +1/+1 counter on it gains shroud until end of turn. (It can't be the target of spells or abilities.)

Three Tree Scribe

Whenever Three Tree Scribe or another creature you control leaves the battlefield without dying, put a +1/+1 counter on target creature you control.

Cloud of Faeries

Flying
When Cloud of Faeries enters, untap up to two lands.
Cycling {2} ({2}, Discard this card: Draw a card.)

Long River Lurker

Ward {1}
Other Frogs you control have ward {1}.
When Long River Lurker enters, target creature you control can't be blocked this turn. Whenever that creature deals combat damage this turn, you may exile it. If you do, return it to the battlefield under its owner's control.

Arcane Signet

{T}: Add one mana of any color in your commander's color identity.

Herald's Horn

As Herald's Horn enters, choose a creature type.
Creature spells you cast of the chosen type cost {1} less to cast.
At the beginning of your upkeep, look at the top card of your library. If it's a creature card of the chosen type, you may reveal it and put it into your hand.

Valley Mightcaller

Trample
Whenever another Frog, Rabbit, Raccoon, or Squirrel you control enters, put a +1/+1 counter on Valley Mightcaller.

Lilysplash Mentor

Reach
{1}{G}{U}: Exile another target creature you control, then return it to the battlefield under its owner's control with a +1/+1 counter on it. Activate only as a sorcery.

Stickytongue Sentinel

Reach
When Stickytongue Sentinel enters, return up to one other target permanent you control to its owner's hand.

Treeguard Duo

When Treeguard Duo enters, until end of turn, target creature you control gains vigilance and gets +X/+X, where X is the number of creatures you control.

Clement, the Worrywort

Vigilance
Whenever Clement, the Worrywort or another creature you control enters, return up to one target creature you control with lesser mana value to its owner's hand.
Frogs you control have "{T}: Add {G} or {U}. Spend this mana only to cast a creature spell."

Splash Portal

Exile target creature you control, then return it to the battlefield under its owner's control. If that creature is a Bird, Frog, Otter, or Rat, draw a card.

Turn to Frog

Until end of turn, target creature loses all abilities and becomes a blue Frog with base power and toughness 1/1.

Polliwallop

This spell costs {1} less to cast for each Frog you control.
Target creature you control deals damage equal to twice its power to target creature you don't control.

Peregrine Drake

Flying
When Peregrine Drake enters, untap up to five lands.

Guardian Project

Whenever a nontoken creature you control enters, if it doesn't have the same name as another creature you control or a creature card in your graveyard, draw a card.

Dour Port-Mage

Whenever one or more other creatures you control leave the battlefield without dying, draw a card.
{1}{U}, {T}: Return another target creature you control to its owner's hand.