Vivien, Monsters' Advocate

You may look at the top card of your library any time.
You may cast creature spells from the top of your library.
+1: Create a 3/3 green Beast creature token. Put your choice of a vigilance counter, a reach counter, or a trample counter on it.
−2: When you next cast a creature spell this turn, search your library for a creature card with lesser mana value, put it onto the battlefield, then shuffle.

Myr Battlesphere

When Myr Battlesphere enters, create four 1/1 colorless Myr artifact creature tokens.
Whenever Myr Battlesphere attacks, you may tap X untapped Myr you control. If you do, Myr Battlesphere gets +X/+0 until end of turn and deals X damage to the player or planeswalker it's attacking.

Jinnie Fay, Jetmir's Second

If you would create one or more tokens, you may instead create that many 2/2 green Cat creature tokens with haste or that many 3/1 green Dog creature tokens with vigilance.

Siege-Gang Commander

When Siege-Gang Commander enters, create three 1/1 red Goblin creature tokens.
{1}{R}, Sacrifice a Goblin: Siege-Gang Commander deals 2 damage to any target.

Ashnod's Altar

Impact Tremors

Whenever a creature you control enters, this enchantment deals 1 damage to each opponent.

Young Pyromancer

Whenever you cast an instant or sorcery spell, create a 1/1 red Elemental creature token.

Symbiotic Elf

When Symbiotic Elf dies, create two 1/1 green Insect creature tokens.

Artifact Mutation

Destroy target artifact. It can't be regenerated. Create X 1/1 green Saproling creature tokens, where X is that artifact's mana value.

Eldritch Evolution

As an additional cost to cast this spell, sacrifice a creature.
Search your library for a creature card with mana value X or less, where X is 2 plus the sacrificed creature's mana value. Put that card onto the battlefield, then shuffle. Exile Eldritch Evolution.

Heartwarming Redemption

Discard all the cards in your hand, then draw that many cards plus one. You gain life equal to the number of cards in your hand.

Witty Roastmaster

Alliance — Whenever another creature you control enters, Witty Roastmaster deals 1 damage to each opponent.

Goldnight Commander

Whenever another creature you control enters, creatures you control get +1/+1 until end of turn.

Gala Greeters

Alliance — Whenever another creature you control enters, choose one that hasn't been chosen this turn —
• Put a +1/+1 counter on Gala Greeters.
• Create a tapped Treasure token.
• You gain 2 life.

Scute Swarm

Landfall — Whenever a land you control enters, create a 1/1 green Insect creature token. If you control six or more lands, create a token that's a copy of Scute Swarm instead.

Elemental Bond

Whenever a creature you control with power 3 or greater enters, draw a card.

Raise the Alarm

Create two 1/1 white Soldier creature tokens.

Midnight Guard

Whenever another creature enters, untap Midnight Guard.

Aura Mutation

Destroy target enchantment. Create X 1/1 green Saproling creature tokens, where X is that enchantment's mana value.

Second Harvest

For each token you control, create a token that's a copy of that permanent.

Academy Manufactor

If you would create a Clue, Food, or Treasure token, instead create one of each.

Chord of Calling

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.)
Search your library for a creature card with mana value X or less, put it onto the battlefield, then shuffle.

Cabaretti Charm

Choose one —
• Cabaretti Charm deals damage equal to the number of creatures you control to target creature or planeswalker.
• Creatures you control get +1/+1 and gain trample until end of turn.
• Create two 1/1 green and white Citizen creature tokens.

Boss's Chauffeur

Boss's Chauffeur enters with a number of +1/+1 counters on it equal to one plus the number of other creatures you control.
Alliance — Whenever another creature you control enters, put a +1/+1 counter on Boss's Chauffeur.
When Boss's Chauffeur dies, create a 1/1 green and white Citizen creature token for each +1/+1 counter on it.

Shared Summons

Search your library for up to two creature cards with different names, reveal them, put them into your hand, then shuffle.

Intangible Virtue

Creature tokens you control get +1/+1 and have vigilance.

Nim Deathmantle

Equipped creature gets +2/+2, has intimidate, and is a black Zombie. (A creature with intimidate can't be blocked except by artifact creatures and/or creatures that share a color with it.)
Whenever a nontoken creature is put into your graveyard from the battlefield, you may pay {4}. If you do, return that card to the battlefield and attach Nim Deathmantle to it.
Equip {4}

Presence of Gond

Enchant creature
Enchanted creature has "{T}: Create a 1/1 green Elf Warrior creature token."

Beetleback Chief

When Beetleback Chief enters, create two 1/1 red Goblin creature tokens.

Prosperous Innkeeper

When Prosperous Innkeeper enters, create a Treasure token. (It's an artifact with "{T}, Sacrifice this artifact: Add one mana of any color.")
Whenever another creature you control enters, you gain 1 life.

Devilish Valet

Trample, haste
Alliance — Whenever another creature you control enters, double Devilish Valet's power until end of turn.

Mycoloth

Devour 2 (As this enters, you may sacrifice any number of creatures. This creature enters with twice that many +1/+1 counters on it.)
At the beginning of your upkeep, create a 1/1 green Saproling creature token for each +1/+1 counter on Mycoloth.

Felidar Retreat

Landfall — Whenever a land you control enters, choose one —
• Create a 2/2 white Cat Beast creature token.
• Put a +1/+1 counter on each creature you control. Those creatures gain vigilance until end of turn.

Geist-Honored Monk

Vigilance
Geist-Honored Monk's power and toughness are each equal to the number of creatures you control.
When Geist-Honored Monk enters, create two 1/1 white Spirit creature tokens with flying.

Sunstrike Legionnaire

Sunstrike Legionnaire doesn't untap during your untap step.
Whenever another creature enters, untap Sunstrike Legionnaire.
{T}: Tap target creature with mana value 3 or less.

Ogre Battledriver

Whenever another creature you control enters, that creature gets +2/+0 and gains haste until end of turn. (It can attack and {T} this turn.)