Ertai's Scorn

This spell costs {U} less to cast if an opponent cast two or more spells this turn.
Counter target spell.

Meletis Astronomer

Heroic — Whenever you cast a spell that targets this creature, look at the top three cards of your library. You may reveal an enchantment card from among them and put it into your hand. Put the rest on the bottom of your library in any order.

Boar Umbra

Enchant creature
Enchanted creature gets +3/+3.
Umbra armor (If enchanted creature would be destroyed, instead remove all damage from it and destroy this Aura.)

Voracious Bibliophile

Flying, vigilance
Whenever you cast a spell with one or more targets, draw that many cards.

Slip Out the Back

Put a +1/+1 counter on target creature. It phases out. (Treat it and anything attached to it as though they don't exist until its controller's next turn.)

Curiosity

Enchant creature
Whenever enchanted creature deals damage to an opponent, you may draw a card.

Snake Umbra

Enchant creature
Enchanted creature gets +1/+1 and has "Whenever this creature deals damage to an opponent, you may draw a card."
Umbra armor (If enchanted creature would be destroyed, instead remove all damage from it and destroy this Aura.)

Rampant Growth

Search your library for a basic land card, put that card onto the battlefield tapped, then shuffle.

Cold-Eyed Selkie

Islandwalk (This creature can't be blocked as long as defending player controls an Island.)
Whenever this creature deals combat damage to a player, you may draw that many cards.

Negate

Ancestral Mask

Enchant creature
Enchanted creature gets +2/+2 for each other enchantment on the battlefield.

Temple of Mystery

This land enters tapped.
When this land enters, scry 1. (Look at the top card of your library. You may put that card on the bottom.)
{T}: Add {G} or {U}.

Tamiyo's Safekeeping

Target permanent you control gains hexproof and indestructible until end of turn. You gain 2 life. (A permanent with hexproof and indestructible can't be the target of spells or abilities your opponents control. Damage and effects that say "destroy" don't destroy it.)

Errant, Street Artist

Flash
Defender, haste
{1}{U}, {T}: Copy target spell you control that wasn't cast. You may choose new targets for the copy.

Souvenir Snatcher

Mutate {5}{U} (If you cast this spell for its mutate cost, put it over or under target non-Human creature you own. They mutate into the creature on top plus all abilities from under it.)
Flying
Whenever this creature mutates, gain control of target noncreature artifact.

Spider Umbra

Enchant creature
Enchanted creature gets +1/+1 and has reach. (It can block creatures with flying.)
Umbra armor (If enchanted creature would be destroyed, instead remove all damage from it and destroy this Aura.)

Cartouche of Knowledge

Enchant creature you control
When this Aura enters, draw a card.
Enchanted creature gets +1/+1 and has flying.

Eldrazi Conscription

Enchant creature
Enchanted creature gets +10/+10 and has trample and annihilator 2. (Whenever it attacks, defending player sacrifices two permanents of their choice.)

Combat Research

Enchant creature
Enchanted creature has "Whenever this creature deals combat damage to a player, draw a card."
As long as enchanted creature is legendary, it gets +1/+1 and has ward {1}. (Whenever enchanted creature becomes the target of a spell or ability an opponent controls, counter it unless that player pays {1}.)

Command Tower

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

Season of Growth

Whenever a creature you control enters, scry 1. (Look at the top card of your library. You may put that card on the bottom.)
Whenever you cast a spell that targets a creature you control, draw a card.

Sawtusk Demolisher

Mutate {3}{G} (If you cast this spell for its mutate cost, put it over or under target non-Human creature you own. They mutate into the creature on top plus all abilities from under it.)
Trample
Whenever this creature mutates, destroy target noncreature permanent. Its controller creates a 3/3 green Beast creature token.

Slip Through Space

Devoid (This card has no color.)
Target creature can't be blocked this turn.
Draw a card.

Scale the Heights

Put a +1/+1 counter on up to one target creature. You gain 2 life. You may play an additional land this turn.
Draw a card.

Irenicus's Vile Duplication

Create a token that's a copy of target creature you control, except the token has flying and it isn't legendary.

Charge Through

Target creature gains trample until end of turn.
Draw a card.

Shielding Plax

({G/U} can be paid with either {G} or {U}.)
Enchant creature
When this Aura enters, draw a card.
Enchanted creature can't be the target of spells or abilities your opponents control.

Rune of Might

Enchant permanent
When this Aura enters, draw a card.
As long as enchanted permanent is a creature, it gets +1/+1 and has trample.
As long as enchanted permanent is an Equipment, it has "Equipped creature gets +1/+1 and has trample."

Elvish Mystic

Double Major

Copy target creature spell you control, except it isn't legendary if the spell is legendary. (A copy of a creature spell becomes a token.)

Sea-Dasher Octopus

Mutate {1}{U} (If you cast this spell for its mutate cost, put it over or under target non-Human creature you own. They mutate into the creature on top plus all abilities from under it.)
Flash
Whenever this creature deals combat damage to a player, draw a card.

Indomitable Might

Flash
Enchant creature
Enchanted creature gets +3/+3.
Enchanted creature's controller may have it assign its combat damage as though it weren't blocked.

Eel Umbra

Flash (You may cast this spell any time you could cast an instant.)
Enchant creature
Enchanted creature gets +1/+1.
Umbra armor (If enchanted creature would be destroyed, instead remove all damage from it and destroy this Aura.)

Abhorrent Oculus

As an additional cost to cast this spell, exile six cards from your graveyard.
Flying
At the beginning of each opponent's upkeep, manifest dread. (Look at the top two cards of your library. Put one onto the battlefield face down as a 2/2 creature and the other into your graveyard. Turn it face up any time for its mana cost if it's a creature card.)

Misty Rainforest

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

Aqueous Form

Enchant creature
Enchanted creature can't be blocked.
Whenever enchanted creature attacks, scry 1. (Look at the top card of your library. You may put that card on the bottom.)

Gnarlback Rhino

Trample (This creature can deal excess combat damage to the player or planeswalker it's attacking.)
Whenever you cast a spell that targets this creature, draw a card.

Artisan of Forms

Heroic — Whenever you cast a spell that targets this creature, you may have this creature become a copy of target creature, except it has this ability.

Replicate

Create a token that's a copy of target creature you control.

Repudiate

Counter target activated or triggered ability. (Mana abilities can't be targeted.)

Repudiate // Replicate

Beast Within

Destroy target permanent. Its controller creates a 3/3 green Beast creature token.

Maraleaf Pixie

Breeding Pool

({T}: Add {G} or {U}.)
As this land enters, you may pay 2 life. If you don't, it enters tapped.

Royal Treatment

Target creature you control gains hexproof until end of turn. Create a Royal Role token attached to that creature. (If you control another Role on it, put that one into the graveyard. Enchanted creature gets +1/+1 and has ward {1}.)

Evacuation

Return all creatures to their owners' hands.

Yavimaya Coast

{T}: Add {C}.
{T}: Add {G} or {U}. This land deals 1 damage to you.

Bear Umbra

Enchant creature
Enchanted creature gets +2/+2 and has "Whenever this creature attacks, untap all lands you control."
Umbra armor (If enchanted creature would be destroyed, instead remove all damage from it and destroy this Aura.)

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.)

Arcane Signet

Llanowar Elves

Cerulean Wisps

Target creature becomes blue until end of turn. Untap that creature.
Draw a card.

Keen Sense

Island

Spellwild Ouphe

Spells that target this creature cost {2} less to cast.

Triton Fortune Hunter

Heroic — Whenever you cast a spell that targets this creature, draw a card.

Snakeskin Veil

Put a +1/+1 counter on target creature you control. It gains hexproof until end of turn. (It can't be the target of spells or abilities your opponents control.)

Trumpeting Gnarr

Mutate {3}{G/U}{G/U} (If you cast this spell for its mutate cost, put it over or under target non-Human creature you own. They mutate into the creature on top plus all abilities from under it.)
Whenever this creature mutates, create a 3/3 green Beast creature token.

Twinning Staff

If you would copy a spell one or more times, instead copy it that many times plus an additional time. You may choose new targets for the additional copy.
{7}, {T}: Copy target instant or sorcery spell you control. You may choose new targets for the copy.

Forest

Ivy, Gleeful Spellthief

Flying
Whenever a player casts a spell that targets only a single creature other than Ivy, you may copy that spell. The copy targets Ivy. (A copy of an Aura spell becomes a token.)

Rancor

Enchant creature
Enchanted creature gets +2/+0 and has trample.
When this Aura is put into a graveyard from the battlefield, return it to its owner's hand.

Viridescent Wisps

Target creature becomes green and gets +1/+0 until end of turn.
Draw a card.

Simic Growth Chamber

This land enters tapped.
When this land enters, return a land you control to its owner's hand.
{T}: Add {G}{U}.

Vesuvan Duplimancy

Whenever you cast a spell that targets only a single artifact or creature you control, create a token that's a copy of that artifact or creature, except it's not legendary.

Sixth Sense

Enchant creature
Enchanted creature has "Whenever this creature deals combat damage to a player, you may draw a card."

Eutropia the Twice-Favored

Constellation — Whenever an enchantment you control enters, put a +1/+1 counter on target creature. That creature gains flying until end of turn.

Rivendell

Rivendell enters tapped unless you control a legendary creature.
{T}: Add {U}.
{1}{U}, {T}: Scry 2. Activate only if you control a legendary creature.

Karametra's Favor

Enchant creature
When this Aura enters, draw a card.
Enchanted creature has "{T}: Add one mana of any color."

Auramancer's Guise

Enchant creature
Enchanted creature gets +2/+2 for each Aura attached to it and has vigilance.

Sanctum Weaver

{T}: Add X mana of any one color, where X is the number of enchantments you control.

Stormchaser Drake

Flying
Whenever this creature becomes the target of a spell you control, draw a card.

Fyndhorn Elves

Shadow Rift

Target creature gains shadow until end of turn. (It can block or be blocked by only creatures with shadow.)
Draw a card.

Exotic Orchard

{T}: Add one mana of any color that a land an opponent controls could produce.

Sol Ring

Glowstone Recluse

Mutate {3}{G} (If you cast this spell for its mutate cost, put it over or under target non-Human creature you own. They mutate into the creature on top plus all abilities from under it.)
Reach
Whenever this creature mutates, put two +1/+1 counters on it.

Gemrazer

Mutate {1}{G}{G} (If you cast this spell for its mutate cost, put it over or under target non-Human creature you own. They mutate into the creature on top plus all abilities from under it.)
Reach, trample
Whenever this creature mutates, destroy target artifact or enchantment an opponent controls.