Island

Seeker of Sunlight

{2}{G}: Seeker of Sunlight explores. Activate only as a sorcery. (Reveal the top card of your library. Put that card into your hand if it's a land. Otherwise, put a +1/+1 counter on this creature, then put the card back or put it into your graveyard.)

Waterwind Scout

Flying
When Waterwind Scout enters, create a Map token. (It's an artifact with "{1}, {T}, Sacrifice this artifact: Target creature you control explores. Activate only as a sorcery.")

River Herald Guide

Vigilance
When River Herald Guide enters, it explores. (Reveal the top card of your library. Put that card into your hand if it's a land. Otherwise, put a +1/+1 counter on this creature, then put the card back or put it into your graveyard.)

Merfolk Cave-Diver

Whenever a creature you control explores, Merfolk Cave-Diver gets +1/+0 until end of turn and can't be blocked this turn.

Council of Echoes

Flying
Descend 4 — When Council of Echoes enters, if there are four or more permanent cards in your graveyard, return up to one target nonland permanent other than Council of Echoes to its owner's hand.

Malamet Battle Glyph

Choose target creature you control and target creature you don't control. If the creature you control entered this turn, put a +1/+1 counter on it. Then those creatures fight each other.

Orazca Puzzle-Door

{1}, {T}, Sacrifice Orazca Puzzle-Door: Look at the top two cards of your library. Put one of those cards into your hand and the other into your graveyard.

Tarrian's Soulcleaver

Equipped creature has vigilance.
Whenever another artifact or creature is put into a graveyard from the battlefield, put a +1/+1 counter on equipped creature.
Equip {2}

Basking Capybara

Descend 4 — Basking Capybara gets +3/+0 as long as there are four or more permanent cards in your graveyard.

Huatli's Final Strike

Target creature you control gets +1/+0 until end of turn. It deals damage equal to its power to target creature an opponent controls.

Nicanzil, Current Conductor

Whenever a creature you control explores a land card, you may put a land card from your hand onto the battlefield tapped.
Whenever a creature you control explores a nonland card, put a +1/+1 counter on Nicanzil, Current Conductor.

Cartographer's Companion

When Cartographer's Companion enters, create a Map token. (It's an artifact with "{1}, {T}, Sacrifice this artifact: Target creature you control explores. Activate only as a sorcery.")

Marauding Brinefang

Ward {3} (Whenever this creature becomes the target of a spell or ability an opponent controls, counter it unless that player pays {3}.)
Islandcycling {2} ({2}, Discard this card: Search your library for an Island card, reveal it, put it into your hand, then shuffle.)

Hidden Nursery

Hidden Nursery enters tapped.
{T}: Add {G}.
{4}{G}, {T}, Sacrifice Hidden Nursery: Discover 4. Activate only as a sorcery. (Exile cards from the top of your library until you exile a nonland card with mana value 4 or less. Cast it without paying its mana cost or put it into your hand. Put the rest on the bottom in a random order.)

Forest

Poison Dart Frog

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

Deepfathom Echo

At the beginning of combat on your turn, Deepfathom Echo explores. Then you may have it become a copy of another creature you control until end of turn. (To have this creature explore, reveal the top card of your library. Put that card into your hand if it's a land. Otherwise, put a +1/+1 counter on this creature, then put the card back or put it into your graveyard.)

Mycoid Maze

(Transforms from Twists and Turns.)
{T}: Add {G}.
{3}{G}, {T}: Look at the top four cards of your library. You may reveal a creature card from among them and put that card into your hand. Put the rest on the bottom of your library in a random order.

Twists and Turns

If a creature you control would explore, instead you scry 1, then that creature explores.
When Twists and Turns enters, target creature you control explores.
When a land you control enters, if you control seven or more lands, transform Twists and Turns.

Twists and Turns // Mycoid Maze

Song of Stupefaction

Enchant creature or Vehicle
When Song of Stupefaction enters, you may mill two cards. (You may put the top two cards of your library into your graveyard.)
Fathomless descent — Enchanted permanent gets -X/-0, where X is the number of permanent cards in your graveyard.

Brackish Blunder

Return target creature to its owner's hand. If it was tapped, create a Map token. (It's an artifact with "{1}, {T}, Sacrifice this artifact: Target creature you control explores. Activate only as a sorcery.")