msem-instigator

Pride Ridge enters tapped.
{T}: Add {G} or {W}.
{2}{G}{W}: Until end of turn, Pride Ridge becomes a Cat creature with vigilance in addition to its other types.
Scavenge {2}{G}{W}

Whenever another creature you control enters, Flightpath Trainee gains flying until end of turn.

{T}, Pay 1 life: Add one mana of any color. Spend this mana only to cast an instant or sorcery spell.

Reclusive Copse enters tapped.
{T}: Add {B} or {G}.
{1}{B}{G}: Until end of turn, Reclusive Copse becomes an Insect creature with deathtouch in addition to its other types.
Scavenge {B}{G}

Search your library for a nonland card, reveal it, and put it into your hand, then shuffle. Until the end of your next turn, spells you cast with the same name as that card cost {3} less to cast.

When Fleshwrithe Ghoul enters, each player sacrifices a creature.
Revive {4}{B} ({4}{B}, Exile this card from your graveyard: Create a token that's a copy of it except it has no mana cost. Revive only as a sorcery.)

Lifelink
When Pact Equivocator enters, you lose 2 life and draw a card.

Mill three cards, then you may return a creature or land card from your graveyard to your hand.

{T}: Add one mana of any color.
Invocation — Whenever you spend four or more mana to cast a spell or activate an ability during your turn, surveil 1. (Look at the top card of your library. You may put it into your graveyard.)

Assault {R} (Whenever this attacks, if it has no +1/+1 counters on it, you may pay its assault cost to put a +1/+1 counter on it.)
When Borsuppa Outrider assaults, it deals 2 damage to each opponent.

Menace (This creature can't be blocked except by two or more creatures.)
Whenever Weedy Whackers attacks, create a 1/1 green Insect creature token that's tapped and attacking.

Flying, trample, lifelink

Flying
Spirited (When this creature enters, you may activate one of its activated abilities without paying its costs.)
{3}{U/B}{U/B}: Look at the top card of target opponent's library, then exile it face down. You may play that card for as long as it remains exiled, and you may spend mana as though it were mana of any type to cast that spell.

Rei, the Supplanter gets +1/+1 for each Forest you control.
At the beginning of each player's end step, if that player didn't play a land this turn, create a Forest token.

{T}, Pay 1 life: Add one mana of any color.

{2}, {T}: Prevent all combat damage that would be dealt to and dealt by target creature this turn.

{7}{R}: Up to three target creatures you control get +3/+0 and gain menace until end of turn. This ability costs {2} less to activate if you control a legendary creature.

When Journey to the Otherworlds enters, draw a card, then choose a creature card name.
Whenever a creature you control with the chosen name attacks, you may aetherize it. (To aetherize, create a token that's a copy of it, then exile that token.)

Slipstream (This creature can't be blocked as long as only creatures with slipstream are attacking.)
Pressure {U} (You may cast this spell for its pressure cost if there are seven or more cards in your graveyard.)

Target creature gains lifelink until end of turn. (Damage dealt by that creature also causes you to gain that much life.)

Once each turn, when you cast a noncreature spell, create a 1/1 colorless Human creature token. Put a prowess counter on it.

When Horizon Treader enters, you may exile target enchantment you control. Return that card to the battlefield under your control at the beginning of the next end step.

Vigilance
Engage (This creature must be blocked each combat if able.)
Other Soldiers you control get +1/+1 and have first strike.

Whenever a creature an opponent controls deals damage to you, monstrosity 2. (If this creature isn't monstrous, put two +1/+1 counters on it and it becomes monstrous.)
Frigid Behemoth can't attack unless it's monstrous.