Turn to Frog

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

Polymorphist's Jest

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

Spore Frog

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

Croaking Counterpart

Create a token that's a copy of target non-Frog creature, except it's a 1/1 green Frog.
Flashback {3}{G}{U} (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Grolnok, the Omnivore

Whenever a Frog you control attacks, mill three cards.
Whenever a permanent card is put into your graveyard from your library, exile it with a croak counter on it.
You may play lands and cast spells from among cards you own in exile with croak counters on them.

Gitrog, Horror of Zhava

Menace
At the beginning of each combat, if Gitrog, Horror of Zhava is untapped, any opponent may sacrifice a nontoken creature. If they do, tap Gitrog, Horror of Zhava, then seek a land card and put it onto the battlefield tapped.
Whenever a land enters under your control, it perpetually gains "{B}{G}, {T}, Sacrifice this land: Draw a card."

Froghemoth

Trample, haste
Whenever Froghemoth deals combat damage to a player, exile up to that many target cards from their graveyard. Put a +1/+1 counter on Froghemoth for each creature card exiled this way. You gain 1 life for each noncreature card exiled this way.

Poison Dart Frog

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

Tatsunari, Toad Rider

Whenever you cast an enchantment spell, if you don't control a creature named Keimi, create Keimi, a legendary 3/3 black and green Frog creature token with "Whenever you cast an enchantment spell, each opponent loses 1 life and you gain 1 life."
{1}{G/U}: Tatsunari, Toad Rider and target Frog you control can't be blocked this turn except by creatures with flying or reach.

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.)

Rapid Hybridization

Destroy target creature. It can't be regenerated. That creature's controller creates a 3/3 green Frog Lizard creature token.

Frogify

Enchant creature
Enchanted creature loses all abilities and is a blue Frog creature with base power and toughness 1/1. (It loses all other card types and creature types.)

Omnibian

{T}: Target creature becomes a Frog with base power and toughness 3/3 until end of turn.

Uurg, Spawn of Turg

Uurg, Spawn of Turg's power is equal to the number of land cards in your graveyard.
At the beginning of your upkeep, surveil 1. (Look at the top card of your library. You may put that card into your graveyard.)
{B}{G}, Sacrifice a land: You gain 2 life.