msem-instigator

As long as Sewer Pack is on the battlefield, you may cast spells named Sewer Pack from your graveyard.
Sewer Pack gets +1/+1 for each other creature on the battlefield named Sewer Pack.

Flash
Harmony — Another target creature gets +1/+0 and gains indestructible until end of turn.
When Siamang Tale-Singer enters, harmonize. (Trigger up to one harmony of a permanent you control.)

Creatures with power less than Sneaking Peak's power can't block it.
At the beginning of your end step, if Sneaking Peak didn't attack this turn, put a +1/+1 counter on it.

When Sorrowslayer enters, put a +1/+1 counter on target creature.
Remove a +1/+1 counter from Sorrowslayer: Trigger a death knell of a permanent you control. Activate only once each turn and only as a sorcery.

Colorless creatures you control have “{T}: Add {C}.”

Trample (This creature can deal excess combat damage to defending player or planeswalker while attacking.)
Sprareos Yearling gets +4/+4 as long as you control five or more lands.

At the beginning of each upkeep, untap up to two target lands.

Hexproof
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.)
As long as Sunrise Sentinel is renowned, other Scouts you control have hexproof.

When Sylvan Explorer enters, reveal the top card of your library. If it's a land card, put it onto the battlefield tapped.

Trample
Death knell — Put a +1/+1 counter on Tempest Dodger. (As a creature you control dies, trigger one death knell of that creature or another permanent you control.)

Voracious 2 (As this enters, you may sacrifice up to two artifacts and/or creatures. This creature enters with that many +1/+1 counters on it.)

When Thallid Cultivator dies, mill four cards. Return a creature card milled this way to your hand.

When Troubled Heir dies, create a tapped Plains token.

When Troubled Homesteader dies, draw a card.

When Urisk Fiddler enters, draw a card.

Melee (Whenever this creature attacks, it gets +1/+1 until end of turn for each opponent you attacked this combat.)
When Vaeldan's Liberator dies, you may exile it. If you do, return a permanent card with mana value less than or equal to Vaeldan's Liberator's power from your graveyard to your hand.

{T}: Add {G}. Spend this mana only to cast a creature spell or activate an ability of a creature.
At the beginning of combat on your turn, if you control a creature with power 4 or greater, Vassal of the Wild gets +2/+1 and gains vigilance until end of turn.

When Village Courier enters, look at the top four cards of your library. You may reveal an artifact, enchantment, or land card from among them and put it into your hand. Put the rest on the bottom of your library in any order.

{T}: Add {G}.
{T}: Sacrifice Visionary Developer: Create a token that's a copy of target token you control. Activate only as a sorcery.

Whenever Voracious Spawn enters or attacks, exile up to one target card from a graveyard. If you exile a permanent card, put a +1/+1 counter on Voracious Spawn. If you exile a nonpermanent card, you gain 1 life.

Walker of the Final Path gets +3/+3 and has trample as long as you control a Horror.
When Walker of the Final Path enters, search your library for a Revelation card, put it into your graveyard, then shuffle.

Whenever a creature you control enters for the second time each turn, you may put a +1/+1 counter on Warren Wardens.

Improve {1} ({1}: Put a +1/+1 counter on this creature. This costs {1} more to activate for each +1/+1 counter on it. Improve only as a sorcery.)
Other creatures you control have improve {1}.

{3}: Wildwood Keeper gets +3/+2 until end of turn. Activate only once each turn.

Experience (Whenever this creature attacks, if it has fewer than three +1/+1 counters on it, put a +1/+1 counter on it.)
When Winding Snake has three or more +1/+1 counters on it, remove them all and transform it.