msem-instigator

Distribute three +1/+1 counters among any number of creatures you control.
Metamorph {1}{G} (You may cast this card face down as a 2/2 creature for {3}. Turn it face up and cast it at any time for its metamorph cost.)

Vigilance
Imisti's Commando can't be blocked by creatures with lesser power.
Whenever Imisti's Commando deals combat damage to a player, draw a card.

Whenever The Ever-Pestilent deals combat damage to a player, that player discards a card at random.

Search your library for a card, put it into your hand, shuffle, then add {B}{R}{G}.
{1}, Discard Tahli's Council: Add one mana of any color. Scry 1.

When Siamang Minstrel enters the battlefield, you may put a lore counter on target Saga you control.

Protection from Dawn Chord (This creature can't be blocked, targeted, dealt damage, or enchanted by anything named Dawn Chord.)
{1}{R}: Target Reflection's base power becomes equal to Dusk Chord's power until end of turn.

Mill four cards. You may put up to two cards from among the milled cards into your hand. Each player loses 2 life.

First strike, lifelink

Hollow Queen can't be blocked by tokens.
Whenever Hollow Queen deals combat damage to a player or planeswalker, you may remove a counter from a permanent you control. If you do, put a +1/+1 counter on target creature you control.

({T}: Add {U} or {B}.)
Sodden Cavern enters the battlefield tapped.

Masked Impersonator can't be blocked.
Art of war — At the beginning of your end step, if Masked Impersonator dealt damage to an opponent this turn, you may have it become a copy of target creature you control except it has this ability.

Whenever you cast a noncreature spell, create a Vial token. (It's an artifact with “{1}, Sacrifice this and another permanent: Draw a card. Activate only during your turn.”)

Whenever another creature named Chef's Apprentice enters the battlefield under your control, target player mills three cards.

Harvest (You may tap any number of creatures you control as you cast this spell. If you do, reduce this spell's mana cost by their total power.)
{T}, Sacrifice a land: Search your library for a land card and put it onto the battlefield, then shuffle.

Target permanent you control gains hexproof until end of turn. If that permanent is a creature, it also gets +1/+1 until end of turn.

{2}{B}{B}, Exile Reclusive Augur from your graveyard: Return another target creature card from your graveyard to the battlefield. Activate only during your turn.

(As this Discovery enters and after your draw step, add a progress counter. Stop after you've discovered.)
I, II — Search your library for a basic land card, reveal it, put it into your hand, then shuffle.
Discovery — {4}: You gain 2 life.

{T}: Add {C}.
{1}, {T}: Add two mana of different colors. Activate only if you control five or more lands.

Rapport — Whenever Hunting Hound and at least one other creature you control become tapped, Hunting Hound gets +2/+0 until end of turn.

Trample, haste
Thriving Hydra enters the battlefield with four +1/+1 counters on it.
When Thriving Hydra enters the battlefield, for each other creature you control, put X +1/+1 counters on that creature, where X is four minus its power.
Whenever Thriving Hydra attacks, double the number of +1/+1 counters on each creature you control.

Encourage ({T}: Another target creature you control gets +1/+1 until end of turn. Encourage only as a sorcery.)
Whenever Blessed Vanquisher encourages a creature, destroy target creature an opponent controls if it's tapped. Otherwise, tap that creature.

When Traversing Bulkvine enters the battlefield, search your library for three land cards with different names and reveal them. An opponent chooses one of them. Put that card into your graveyard and the rest into your hand, then shuffle.

Puzzlebox (Begin the game with this and another card you own from outside the game in the command zone, locked. That card is face down until you unlock this.)
{2}, Discard your hand: Unlock Traitor's Gambit. If the revealed card is red, put it into your hand. Otherwise, put it on top of your library.

[+1]: Tanya, the Mooncursed becomes a legendary 3/1 red Werewolf creature with first strike until end of turn.
[–2]: Tanya, the Mooncursed deals 3 damage to target creature or planeswalker.
[–4]: Destroy target nonbasic colorless permanent.

{1}, Sacrifice Wayfarer's Amulet: Search your library for a basic land card, reveal it, put it into your hand, then shuffle.
{3}, Sacrifice Wayfarer's Amulet: Search your library for a riddle card, reveal it, put it into your hand, then shuffle.