msem-instigator

Whenever The Dreamer enters or you play a card exiled with them, exile the top two cards of your library face down, then another face up.
You may play face up cards exiled with The Dreamer.
{T}, Sacrifice The Dreamer: Look at each face down card exiled with The Dreamer. You may cast one without paying its mana cost.

Other creatures have haste and attack each combat if able.
Nonland cards in your hand have paranoia {4}. (The owner of a card with paranoia {4} may cast it from their hand for {4} when a permanent they control leaves the battlefield.)

Flying
Spirited (When this creature enters, you may activate one of its activated abilities without paying its cost.)
{3}{R}{R}, {T}: Exile an instant card with mana value 3 or less from your graveyard, then cast a copy of a card exiled with Thunderlash Mystic without paying its mana cost.

Harmony — Creatures you control gain double strike until end of turn.
When Twirling Duet enters, harmonize. (Trigger up to one harmony of one permanent you control.)

This spell costs {2} less to cast if your starting deck contained at least forty cards more than the minimum deck size.
When Unrivaled Fireweaver enters, you may exile a red instant or sorcery card you own from outside the game. Until the end of your next turn, you may play that card.

Renown 1 (When this creature deals combat damage to a player, if it isn't renowned, put a +1/+1 counter on it and it becomes renowned.)
Whenever a creature you control becomes renowned, create a 1/1 red Soldier creature token with haste.

Flying, haste
{R}: Varagan Wyrmling gets +1/+0 until end of turn. Activate this ability only up to three times each turn.

Flying, haste
Venwyn, the Dragon's Fang can't block.
At the beginning of combat on your turn, you may pay {1}{R/G}. If you do, create a token that's a copy of target creature you control with mana value 3 or less, except it's not legendary and has haste. Exile that token at end of combat.

Rhapsody {3}{R}{R} (Pay {3}{R}{R} to cast this as a 4/4, or as a sorcery to make it become a 4/4.)
Whenever Vindictive Guardian or another creature you control enters, if that creature's power is 4 or greater, create a Treasure token.

When Visiting Dignitary enters, gain control of target creature until end of turn. Untap that creature. It gains haste until end of turn.

Eureka! (At the beginning of each end step, you get a research counter if you cast a spell this turn. Then if you have eight or more research counters, remove them and create a Masterpiece token of your choice.)
Whenever an artifact you control enters, up to two target creatures get +1/+0 and haste until end of turn.

When Wavebreaker enters, add two mana of any one color. You can't spend this mana to cast spells.

Whenever you cast a Knight spell or an Adventure spell, Wimbledon's Squire gets +1/+1 until end of turn.

Transcend (Activate as a sorcery to gain the next type and a +1/+1 counter.)
Trample
{2}{R}: Demigod — Create a 2/1 black Spirit creature token with “This creature can't block.”
{5}{R}: God — Until end of turn, creatures you control get +1/+0 and gain haste and “When this creature dies, it deals 1 damage to any target.”

At the beginning of combat on your turn, you may pay {2}{R}{R}. If you do, create a 4/4 red Dragon creature token with flying and haste. Exile that token at end of combat.
Ferocious — Whenever Xiusheng of the Dragon Realm attacks, if you control a creature with power 4 or greater, Xiusheng gains double strike until end of turn.

Flying
Erratic (When this creature dies, reveal the top four cards of your library. Put a creature card that costs less than this revealed this way onto the battlefield and the rest on the bottom of your library in any order.)
Whenever Zaidha, Seraph of Calamity deals combat damage to a player, choose up to two target nonland permanents that player controls and target nonland permanent you control. Destroy one of those permanents at random.

Creature tokens you control have hexproof.
{3}{G}: Put a +1/+1 counter on target creature token.

Heretic (Whenever you cast a spell that doesn't share a color with this creature, it gets +1/+1 until end of turn.)
Discard a card: Abominable Mongrel gets +1/+1 and becomes the color of your choice until end of turn.

Trample
Other Hounds you control get +1/+1 and have trample.

Frenzy 2 (Whenever this creature attacks and isn't blocked, it gets +2/+0 until end of turn.)
Whenever Airam, Packleader becomes blocked, other creatures you control get +1/+1 until end of turn.

Infamy 1 (Whenever this creature deals combat damage to a player, if it has no +1/+1 counters on it, put a +1/+1 counter on it and it becomes infamous.)
When Alpha Scout becomes infamous, create a 2/2 green Wolf creature token.

{T}, Reveal an Angel card from your hand: For each of that card's colors, add one mana of that color.

Whenever Angeltouched Dryad or another permanent you control is turned face up, add {C}{C}.
Morph {2} (You may cast this card face down as a 2/2 creature for {3}. Turn it face up any time for its morph cost.)

When Apprentice Summoner enters, search your library for a creature card with mana value 1 or less, put it onto the battlefield, then shuffle.