msem-instigator

{G}, {T}: Add one mana of any color. When a creature enters this turn, if that mana was spent to cast it, it explores. (Reveal the top card of your library. Put that card into your hand if it's a land. Otherwise, put a +1/+1 counter on this creature, then put the card back or put it into your graveyard.)

Tortle Traveler enters tapped.
When Tortle Traveler enters, it explores. (Reveal the top card of your library. Put that card into your hand if it's a land. Otherwise, put a +1/+1 counter on this creature, then put the card back or put it into your graveyard.)

Target player gets a poison counter.
Draw a card.

Search your library for a card. You may cast it without paying its mana cost if it's a green creature or Revelation spell with mana value X or less. Then shuffle.
Coalesce {X}{X}{G}{G}{G}{G} (You may cast this from your graveyard for {X}{X}{G}{G}{G}{G}. If you do, it enters as a Horror creature after it resolves. Exile it if it would leave the battlefield or not resolve.)

Towering Inferno deals X damage to each creature without flying. If a creature you don't control dealt damage this way would die this turn, exile it instead.

{1}{W}, Sacrifice Town Elder: Return target artifact or enchantment card from your graveyard to your hand.

Deathtouch
Heretic (Whenever you cast a spell that doesn't share a color with this creature, it gets +1/+1 until end of turn.)

Enchant creature
Enchanted creature has hexproof.
{U}: Enchanted creature can't be blocked by target creature this turn.

Untap target creature. It gets +2/+2 and gains hexproof until end of turn.

Tracking Party enters with a +1/+1 counter on it.
{T}, Remove a +1/+1 counter from Tracking Party and exert it: Destroy target artifact or enchantment. (An exerted creature won't untap during your next untap step.)

Target creature you control fights target creature you don't control, then fights it again.

Flash
When Trade Route Bandit enters, you may have each player draw two cards.

Frenzy 1 (Whenever this creature attacks and isn't blocked, it gets +1/+0 until end of turn.)
Whenever Trading Traitor deals combat damage to a player, you lose life equal to the number of unblocked attacking creatures you control and draw that many cards.

Ward {2} (Whenever this creature becomes the target of a spell or ability an opponent controls, counter it unless that player pays {2}.)
{2}{W}{W}, Return an unblocked attacking creature you control to its owner's hand: Create a 4/4 white Angel creature token with flying that's tapped and attacking.

Haste
Sacrifice a land: Trail Blazer explores. You may put a basic land card from your hand onto the battlefield tapped. (Reveal the top card of your library. Put it into your hand if it's a land. Otherwise, put a +1/+1 counter on this creature, then you may put that card in your graveyard.)

Put target permanent card from your graveyard on top of your library.

Whenever a basic land you control enters, add one mana of any color.

Vanguard — Whenever a creature you control attacks alone, draw a card.

Each creature you control enters with an additional +1/+1 counter on it.
When Training Sim enters, create a Function token with “Target creature you control fights target creature you don't control.” (It's an enchantment. As you cast an instant or sorcery spell, sacrifice any number of Functions to add their effects to that spell.)

Whenever a creature you control attacks and isn't blocked, it explores. (Reveal the top card of your library. Put that card into your hand if it's a land. Otherwise, put a +1/+1 counter on that creature, then put the card back or put it into your graveyard.)

When Transcended Explorer enters, if you control another enchantment, draw a card.

Enchant creature
When Transcendent Arts enters, draw a card.
Enchanted creature can't be blocked by creatures that don't share a creature type with it.

You may exile a land card from your hand rather than pay this spell's mana cost.

Reveal the top four cards of your library. You may put a creature or Revelation card from among them into your hand. Put the rest into your graveyard.

When Transformative Paints enters, create a 1/1 white Human creature token, then attach Transformative Paints to it.
Equipped creature gets +1/+0 and has prowess.
Equip {3}