Maralen, Fae Ascendant

Flying
Whenever Maralen or another Elf or Faerie you control enters, exile the top two cards of target opponent's library.
Once each turn, you may cast a spell with mana value less than or equal to the number of Elves and Faeries you control from among cards exiled with Maralen this turn without paying its mana cost.

Formidable Speaker

When this creature enters, you may discard a card. If you do, search your library for a creature card, reveal it, put it into your hand, then shuffle.
{1}, {T}: Untap another target permanent.

Wistfulness

When this creature enters, if {G}{G} was spent to cast it, exile target artifact or enchantment an opponent controls.
When this creature enters, if {U}{U} was spent to cast it, draw two cards, then discard a card.
Evoke {G/U}{G/U} (You may cast this spell for its evoke cost. If you do, it's sacrificed when it enters.)

Kinscaer Sentry

First strike, lifelink
Whenever this creature attacks, you may put a creature card with mana value X or less from your hand onto the battlefield tapped and attacking, where X is the number of attacking creatures you control.

Raiding Schemes

Each noncreature spell you cast has conspire. (As you cast a noncreature spell, you may tap two untapped creatures you control that share a color with it. When you do, copy it and you may choose new targets for the copy. A copy of a permanent spell becomes a token.)

Hallowed Fountain

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

Glen Elendra's Answer

This spell can't be countered.
Counter all spells your opponents control and all abilities your opponents control. Create a 1/1 blue and black Faerie creature token with flying for each spell and ability countered this way.

End-Blaze Epiphany

End-Blaze Epiphany deals X damage to target creature. When that creature dies this turn, exile a number of cards from the top of your library equal to its power, then choose a card exiled this way. Until the end of your next turn, you may play that card.

Trystan, Penitent Culler

Deathtouch
Whenever this creature transforms into Trystan, Penitent Culler, mill three cards, then you may exile an Elf card from your graveyard. If you do, each opponent loses 2 life.
At the beginning of your first main phase, you may pay {G}. If you do, transform Trystan.

Trystan, Callous Cultivator

Deathtouch
Whenever this creature enters or transforms into Trystan, Callous Cultivator, mill three cards. Then if there is an Elf card in your graveyard, you gain 2 life.
At the beginning of your first main phase, you may pay {B}. If you do, transform Trystan.

Trystan, Callous Cultivator // Trystan, Penitent Culler

Trystan's Command

Choose two —
• Create a token that's a copy of target Elf you control.
• Return one or two target permanent cards from your graveyard to your hand.
• Destroy target creature or enchantment.
• Creatures target player controls get +3/+3 until end of turn. Untap them.

Sanar, Innovative First-Year

Vivid — At the beginning of your first main phase, reveal cards from the top of your library until you reveal X nonland cards, where X is the number of colors among permanents you control. For each of those colors, you may exile a card of that color from among the revealed cards. Then shuffle. You may cast the exiled cards this turn.

Champion of the Clachan

Flash
As an additional cost to cast this spell, behold a Kithkin and exile it. (Exile a Kithkin you control or a Kithkin card from your hand.)
Other Kithkin you control get +1/+1.
When this creature leaves the battlefield, return the exiled card to its owner's hand.

Bre of Clan Stoutarm

{1}{W}, {T}: Another target creature you control gains flying and lifelink until end of turn.
At the beginning of your end step, if you gained life this turn, exile cards from the top of your library until you exile a nonland card. You may cast that card without paying its mana cost if the spell's mana value is less than or equal to the amount of life you gained this turn. Otherwise, put it into your hand.

Rimefire Torque

As this artifact enters, choose a creature type.
Whenever a permanent you control of the chosen type enters, put a charge counter on this artifact.
{T}, Remove three charge counters from this artifact: When you next cast an instant or sorcery spell this turn, copy it. You may choose new targets for the copy.

Adept Watershaper

Other tapped creatures you control have indestructible.

Mutable Explorer

Changeling (This card is every creature type.)
When this creature enters, create a tapped Mutavault token. (It's a land with "{T}: Add {C}" and "{1}: This token becomes a 2/2 creature with all creature types until end of turn. It's still a land.")

Ashling, Rimebound

Whenever this creature transforms into Ashling, Rimebound and at the beginning of your first main phase, add two mana of any one color. Spend this mana only to cast spells with mana value 4 or greater.
At the beginning of your first main phase, you may pay {R}. If you do, transform Ashling.

Ashling, Rekindled

Whenever this creature enters or transforms into Ashling, Rekindled, you may discard a card. If you do, draw a card.
At the beginning of your first main phase, you may pay {U}. If you do, transform Ashling.

Ashling, Rekindled // Ashling, Rimebound

Selfless Safewright

Flash
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.)
When this creature enters, choose a creature type. Other permanents you control of that type gain hexproof and indestructible until end of turn.

Blood Crypt

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

Champion of the Path

As an additional cost to cast this spell, behold an Elemental and exile it. (Exile an Elemental you control or an Elemental card from your hand.)
Whenever another Elemental you control enters, it deals damage equal to its power to each opponent.
When this creature leaves the battlefield, return the exiled card to its owner's hand.

Disruptor of Currents

Flash
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.)
When this creature enters, return up to one other target nonland permanent to its owner's hand.

Bristlebane Battler

Trample, ward {2}
This creature enters with five -1/-1 counters on it.
Whenever another creature you control enters while this creature has a -1/-1 counter on it, remove a -1/-1 counter from this creature.