Most Valuable Slayer

Whenever you attack, target attacking creature gets +1/+0 and gains first strike until end of turn.

Plains

Toby, Beastie Befriender

When Toby, Beastie Befriender enters, create a 4/4 white Beast creature token with "This creature can't attack or block alone."
As long as you control four or more creature tokens, creature tokens you control have flying.

Sheltered by Ghosts

Enchant creature you control
When Sheltered by Ghosts enters, exile target nonland permanent an opponent controls until Sheltered by Ghosts leaves the battlefield.
Enchanted creature gets +1/+0 and has lifelink and ward {2}.

Hardened Escort

Whenever Hardened Escort attacks, another target creature you control gets +1/+0 and gains indestructible until end of turn. (Damage and effects that say "destroy" don't destroy it.)

Impossible Inferno

Impossible Inferno deals 6 damage to target creature.
Delirium — If there are four or more card types among cards in your graveyard, exile the top card of your library. You may play it until the end of your next turn.

Seized from Slumber

This spell costs {3} less to cast if it targets a tapped creature.
Destroy target creature.

Ghostly Dancers

Flying
When Ghostly Dancers enters, return an enchantment card from your graveyard to your hand or unlock a locked door of a Room you control.
Eerie — Whenever an enchantment you control enters and whenever you fully unlock a Room, create a 3/1 white Spirit creature token with flying.

Mountain

Shattered Yard

At the beginning of your end step, this Room deals 1 damage to each opponent.
(You may cast either half. That door unlocks on the battlefield. As a sorcery, you may pay the mana cost of a locked door to unlock it.)

Glassworks

When you unlock this door, this Room deals 4 damage to target creature an opponent controls.
(You may cast either half. That door unlocks on the battlefield. As a sorcery, you may pay the mana cost of a locked door to unlock it.)

Glassworks // Shattered Yard

The Jolly Balloon Man

Haste
{1}, {T}: Create a token that's a copy of another target creature you control, except it's a 1/1 red Balloon creature in addition to its other colors and types and it has flying and haste. Sacrifice it at the beginning of the next end step. Activate only as a sorcery.

Scorching Dragonfire

Scorching Dragonfire deals 3 damage to target creature or planeswalker. If that creature or planeswalker would die this turn, exile it instead.

Betrayer's Bargain

As an additional cost to cast this spell, sacrifice a creature or enchantment or pay {2}.
Betrayer's Bargain deals 5 damage to target creature. If that creature would die this turn, exile it instead.

Splitskin Doll

When Splitskin Doll enters, draw a card. Then discard a card unless you control another creature with power 2 or less.

Enduring Innocence

Lifelink
Whenever one or more other creatures you control with power 2 or less enter, draw a card. This ability triggers only once each turn.
When Enduring Innocence dies, if it was a creature, return it to the battlefield under its owner's control. It's an enchantment. (It's not a creature.)

Fear of Surveillance

Vigilance
Whenever Fear of Surveillance attacks, surveil 1. (Look at the top card of your library. You may put it into your graveyard.)

Possessed Goat

{3}, Discard a card: Put three +1/+1 counters on Possessed Goat and it becomes a black Demon in addition to its other colors and types. Activate only once.

Hand That Feeds

Delirium — Whenever Hand That Feeds attacks while there are four or more card types among cards in your graveyard, it gets +2/+0 and gains menace until end of turn. (It can't be blocked except by two or more creatures.)

Trapped in the Screen

Ward {2} (Whenever this enchantment becomes the target of a spell or ability an opponent controls, counter it unless that player pays {2}.)
When Trapped in the Screen enters, exile target artifact, creature, or enchantment an opponent controls until Trapped in the Screen leaves the battlefield.

Glimmerlight

When Glimmerlight enters, create a 1/1 white Glimmer enchantment creature token.
Equipped creature gets +1/+1.
Equip {1} ({1}: Attach to target creature you control. Equip only as a sorcery.)

Acrobatic Cheerleader

Survival — At the beginning of your second main phase, if Acrobatic Cheerleader is tapped, put a flying counter on it. This ability triggers only once.

Clockwork Percussionist

Haste
When Clockwork Percussionist dies, exile the top card of your library. You may play it until the end of your next turn.

Chainsaw

When Chainsaw enters, it deals 3 damage to up to one target creature.
Whenever one or more creatures die, put a rev counter on Chainsaw.
Equipped creature gets +X/+0, where X is the number of rev counters on Chainsaw.
Equip {3}