Mastery of the Unseen

Whenever a permanent you control is turned face up, you gain 1 life for each creature you control.
{3}{W}: Manifest the top card of your library. (Put it onto the battlefield face down as a 2/2 creature. Turn it face up any time for its mana cost if it's a creature card.)

Ugin, the Ineffable

Colorless spells you cast cost {2} less to cast.
+1: Exile the top card of your library face down and look at it. Create a 2/2 colorless Spirit creature token. When that token leaves the battlefield, put the exiled card into your hand.
−3: Destroy target permanent that's one or more colors.

Nylea, Keen-Eyed

Indestructible
As long as your devotion to green is less than five, Nylea isn't a creature.
Creature spells you cast cost {1} less to cast.
{2}{G}: Reveal the top card of your library. If it's a creature card, put it into your hand. Otherwise, you may put it into your graveyard.

Monk Class

(Gain the next level as a sorcery to add its ability.)
The second spell you cast each turn costs {1} less to cast.
{W}{U}: Level 2
When this Class becomes level 2, return up to one target nonland permanent to its owner's hand.
{1}{W}{U}: Level 3
At the beginning of your upkeep, exile the top card of your library. For as long as it remains exiled, it has "You may cast this card from exile as long as you've cast another spell this turn."

Temur War Shaman

When Temur War Shaman enters the battlefield, manifest the top card of your library. (Put that card onto the battlefield face down as a 2/2 creature. Turn it face up any time for its mana cost if it's a creature card.)
Whenever a permanent you control is turned face up, if it's a creature, you may have it fight target creature you don't control.

Semblance Anvil

Imprint — When Semblance Anvil enters the battlefield, you may exile a nonland card from your hand.
Spells you cast that share a card type with the exiled card cost {2} less to cast.

Heartless Summoning

Creature spells you cast cost {2} less to cast.
Creatures you control get -1/-1.

Cemetery Prowler

Vigilance
Whenever Cemetery Prowler enters the battlefield or attacks, exile a card from a graveyard.
Spells you cast cost {1} less to cast for each card type they share with cards exiled with Cemetery Prowler.

Wilderness Reclamation

At the beginning of your end step, untap all lands you control.

Awakening

At the beginning of each upkeep, untap all creatures and lands.

Trail of Mystery

Whenever a face-down creature enters the battlefield under your control, you may search your library for a basic land card, reveal it, put it into your hand, then shuffle.
Whenever a permanent you control is turned face up, if it's a creature, it gets +2/+2 until end of turn.

Ixidron

As Ixidron enters the battlefield, turn all other nontoken creatures face down. (They're 2/2 creatures.)
Ixidron's power and toughness are each equal to the number of face-down creatures on the battlefield.

Bonethorn Valesk

Whenever a permanent is turned face up, Bonethorn Valesk deals 1 damage to any target.

Obscuring Aether

Face-down creature spells you cast cost {1} less to cast.
{1}{G}: Turn Obscuring Aether face down. (It becomes a 2/2 creature.)

Dream Chisel

Face-down creature spells you cast cost {1} less to cast.

Ghostfire Blade

Equipped creature gets +2/+2.
Equip {3}
Ghostfire Blade's equip ability costs {2} less to activate if it targets a colorless creature.

Seedborn Muse

Untap all permanents you control during each other player's untap step.

Rakdos, Lord of Riots

You can't cast this spell unless an opponent lost life this turn.
Flying, trample
Creature spells you cast cost {1} less to cast for each 1 life your opponents have lost this turn.

Centaur Omenreader

As long as Centaur Omenreader is tapped, creature spells you cast cost {2} less to cast.

Ixidor, Reality Sculptor

Face-down creatures get +1/+1.
{2}{U}: Turn target face-down creature face up.

Cloud Key

As Cloud Key enters the battlefield, choose artifact, creature, enchantment, instant, or sorcery.
Spells you cast of the chosen type cost {1} less to cast.

Skirk Alarmist

Haste
{T}: Turn target face-down creature you control face up. At the beginning of the next end step, sacrifice it.

Qarsi Deceiver

{T}: Add {C}. Spend this mana only to cast a face-down creature spell, pay a mana cost to turn a manifested creature face up, or pay a morph cost. (A megamorph cost is a morph cost.)

Urban Burgeoning

Enchant land
Enchanted land has "Untap this land during each other player's untap step."

Secret Plans

Face-down creatures you control get +0/+1.
Whenever a permanent you control is turned face up, draw a card.

Aphetto Runecaster

Whenever a permanent is turned face up, you may draw a card.

Aven Farseer

Flying
Whenever a permanent is turned face up, put a +1/+1 counter on Aven Farseer.

Marauding Raptor

Creature spells you cast cost {1} less to cast.
Whenever another creature enters the battlefield under your control, Marauding Raptor deals 2 damage to it. If a Dinosaur is dealt damage this way, Marauding Raptor gets +2/+0 until end of turn.

Herald of Kozilek

Devoid (This card has no color.)
Colorless spells you cast cost {1} less to cast.