Spontaneous Mutation

Flash
Enchant creature
Enchanted creature gets -X/-0, where X is the number of cards in your graveyard.

One with the Stars

Enchant creature or enchantment
Enchanted permanent is an enchantment and loses all other card types. (It still has its abilities, but it's no longer a creature.)

Vineweft

Enchant creature
Enchanted creature gets +1/+1.
{4}{G}: Return Vineweft from your graveyard to your hand.

Psychic Impetus

Enchant creature
Enchanted creature gets +2/+2 and is goaded. (It attacks each combat if able and attacks a player other than you if able.)
Whenever enchanted creature attacks, you scry 2.

Charmed Sleep

Enchant creature
When Charmed Sleep enters the battlefield, tap enchanted creature.
Enchanted creature doesn't untap during its controller's untap step.

Island

Gift of Paradise

Enchant land
When Gift of Paradise enters the battlefield, you gain 3 life.
Enchanted land has "{T}: Add two mana of any one color."

Interpret the Signs

Scry 3, then reveal the top card of your library. Draw cards equal to that card's mana value. (To scry 3, look at the top three cards of your library, then put any number of them on the bottom of your library and the rest on top in any order.)

Forest

Setessan Training

Enchant creature you control
When Setessan Training enters the battlefield, draw a card.
Enchanted creature gets +1/+0 and has trample. (It can deal excess combat damage to the player or planeswalker it's attacking.)

Capture Sphere

Flash (You may cast this spell any time you could cast an instant.)
Enchant creature
When Capture Sphere enters the battlefield, tap enchanted creature.
Enchanted creature doesn't untap during its controller's untap step.

Library Larcenist

Whenever Library Larcenist attacks, draw a card.

Prying Eyes

Omenspeaker

When Omenspeaker enters the battlefield, scry 2. (Look at the top two cards of your library, then put any number of them on the bottom of your library and the rest on top in any order.)

Eutropia the Twice-Favored

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

Stratus Walk

Enchant creature
When Stratus Walk enters the battlefield, draw a card.
Enchanted creature has flying. (It can't be blocked except by creatures with flying or reach.)
Enchanted creature can block only creatures with flying.

Containment Membrane

Surge {U} (You may cast this spell for its surge cost if you or a teammate has cast another spell this turn.)
Enchant creature
Enchanted creature doesn't untap during its controller's untap step.

Setessan Skirmisher

Constellation — Whenever an enchantment enters the battlefield under your control, Setessan Skirmisher gets +1/+1 until end of turn.

Brine Giant

This spell costs {1} less to cast for each enchantment you control.

Klothys's Design

Creatures you control get +X/+X until end of turn, where X is your devotion to green. (Each {G} in the mana costs of permanents you control counts toward your devotion to green.)

Spellkeeper Weird

{2}, {T}, Sacrifice Spellkeeper Weird: Return target instant or sorcery card from your graveyard to your hand.

Sailor of Means

When Sailor of Means enters the battlefield, create a Treasure token. (It's an artifact with "{T}, Sacrifice this artifact: Add one mana of any color.")

Starlit Mantle

Flash
Enchant creature you control
When Starlit Mantle enters the battlefield, enchanted creature gains hexproof until end of turn. (It can't be the target of spells or abilities your opponents control.)
Enchanted creature gets +1/+1.

Floodtide Serpent

Floodtide Serpent can't attack unless you return an enchantment you control to its owner's hand. (This cost is paid as attackers are declared.)

Nyxborn Colossus

Paralyzing Grasp

Enchant creature
Enchanted creature doesn't untap during its controller's untap step.

Ichthyomorphosis

Enchant creature
Enchanted creature loses all abilities and is a blue Fish with base power and toughness 0/1.

Bubble Snare

Kicker {2}{U} (You may pay an additional {2}{U} as you cast this spell.)
Enchant creature
When Bubble Snare enters the battlefield, if it was kicked, tap enchanted creature.
Enchanted creature doesn't untap during its controller's untap step.

Sea Legs

Flash
Enchant creature
Enchanted creature gets +0/+2 as long as it's a Pirate. Otherwise, it gets -2/-0.

Clockwork Servant

Adamant — When Clockwork Servant enters the battlefield, if at least three mana of the same color was spent to cast it, draw a card.

Witness of Tomorrows

Temur Runemark

Enchant creature
Enchanted creature gets +2/+2.
Enchanted creature has trample as long as you control a blue or red permanent.

Runner's Bane

Enchant creature with power 3 or less
When Runner's Bane enters the battlefield, tap enchanted creature.
Enchanted creature doesn't untap during its controller's untap step.

Arrester's Admonition

Return target creature to its owner's hand.
Addendum — If you cast this spell during your main phase, draw a card.

Vow of Wildness

Enchant creature
Enchanted creature gets +3/+3, has trample, and can't attack you or planeswalkers you control.

Tall as a Beanstalk

Enchant creature
Enchanted creature gets +3/+3, has reach, and is a Giant in addition to its other types.

Shimmerwing Chimera

Flying
At the beginning of your upkeep, return up to one other target enchantment you control to its owner's hand.

Borderland Ranger

When Borderland Ranger enters the battlefield, you may search your library for a basic land card, reveal it, put it into your hand, then shuffle.

Unquenchable Thirst

Enchant creature
When Unquenchable Thirst enters the battlefield, if you control a Desert or there is a Desert card in your graveyard, tap enchanted creature.
Enchanted creature doesn't untap during its controller's untap step.

Moonlit Scavengers

When Moonlit Scavengers enters the battlefield, if you control an artifact or enchantment, return target creature an opponent controls to its owner's hand.

Ior Ruin Expedition

Landfall — Whenever a land enters the battlefield under your control, you may put a quest counter on Ior Ruin Expedition.
Remove three quest counters from Ior Ruin Expedition and sacrifice it: Draw two cards.

Reckless Amplimancer

{4}{G}: Double Reckless Amplimancer's power and toughness until end of turn.

Sea God's Scorn

Return up to three target creatures and/or enchantments to their owners' hands.

Skygames

Enchant land
Enchanted land has "{T}: Target creature gains flying until end of turn. Activate only as a sorcery."

Nyx Herald

At the beginning of combat on your turn, target enchanted creature or enchantment creature you control gets +1/+1 and gains trample until end of turn.

Eidolon of Philosophy

{6}{U}, Sacrifice Eidolon of Philosophy: Draw three cards.

Roots

Enchant creature without flying
When Roots enters the battlefield, tap enchanted creature.
Enchanted creature doesn't untap during its controller's untap step.

Arachnoform

Enchant creature
Enchanted creature gets +2/+2, has reach, and is every creature type.

Warbriar Blessing

Enchant creature you control
When Warbriar Blessing enters the battlefield, enchanted creature fights up to one target creature you don't control. (Each deals damage equal to its power to the other.)
Enchanted creature gets +0/+2.

Bind the Monster

Enchant creature
When Bind the Monster enters the battlefield, tap enchanted creature. It deals damage to you equal to its power.
Enchanted creature doesn't untap during its controller's untap step.

Horizon Seeker

Boast — {1}{G}: Search your library for a basic land card, reveal it, put it into your hand, then shuffle. (Activate only if this creature attacked this turn and only once each turn.)

So Tiny

Flash
Enchant creature
Enchanted creature gets -2/-0. It gets -6/-0 instead as long as its controller has seven or more cards in their graveyard.

Siege Wurm

Convoke (Your creatures can help cast this spell. Each creature you tap while casting this spell pays for {1} or one mana of that creature's color.)
Trample

Dwindle

Enchant creature
Enchanted creature gets -6/-0.
When enchanted creature blocks, destroy it. (The attacking creature remains blocked.)

Mists of Littjara

Flash
Enchant creature or Vehicle
Enchanted creature gets -3/-0.

Nexus Wardens

Reach
Constellation — Whenever an enchantment enters the battlefield under your control, you gain 2 life.

Frost Lynx

When Frost Lynx enters the battlefield, tap target creature an opponent controls. That creature doesn't untap during its controller's next untap step.

Howling Golem

Whenever Howling Golem attacks or blocks, each player draws a card.

Chillbringer

Flying
When Chillbringer enters the battlefield, tap target creature an opponent controls. It doesn't untap during its controller's next untap step.

Claustrophobia

Enchant creature
When Claustrophobia enters the battlefield, tap enchanted creature.
Enchanted creature doesn't untap during its controller's untap step.

Nyxborn Triton

Bestow {4}{U} (If you cast this card for its bestow cost, it's an Aura spell with enchant creature. It becomes a creature again if it's not attached to a creature.)
Enchanted creature gets +2/+3.

Feral Invocation

Flash (You may cast this spell any time you could cast an instant.)
Enchant creature
Enchanted creature gets +2/+2.

Glittering Frost

Enchant land
Enchanted land is snow.
Whenever enchanted land is tapped for mana, its controller adds an additional one mana of any color.

Triton Waverider

Constellation — Whenever an enchantment enters the battlefield under your control, Triton Waverider gains flying until end of turn.