msem-instigator

As an additional cost to cast this spell, discard a land card.
Exile the top two cards of your library. Until end of turn, you may play those cards.

Triumphant Return deals 3 damage to up to one target creature. You may put an exiled creature card you own that's on an Adventure into your hand.

Rhapsody {4}{R}{R} (Pay {4}{R}{R} to cast this as a 4/4, or as a sorcery to make it become a 4/4.)
Double strike

Flying
When Trove Keeper dies, create two Treasure tokens.

Flying
When Trove Tyrant enters, exile the top five cards of your library.
Whenever Trove Tyrant deals combat damage to a player, you may cast an artifact card exiled with it without paying its mana cost.

Whenever Trusted Comrade and at least one other creature attack, create a 1/1 white Soldier creature token that's tapped and attacking.

When Truthseeker's Blade enters, it deals 2 damage to target creature you don't control.
Equipped creature gets +2/+0.
Equip {3}

Choose one —
• When you next cast an instant or sorcery spell this turn, copy that spell. You may choose new targets for the copy.
• Target creature you control gains double strike until end of turn

Flying
Whenever you tap a Mountain for mana, add {R} and that land deals 1 damage to you.
Whenever you tap a non-Mountain land for mana, that land deals 1 damage to Tseng, Warden of the Peak.

Flying
Lands you control have “{T}: Add {R}{R}. This land deals 2 damage to you.”
{R}{R}{R}{R}{R}{R}: Shuffle your library, then exile the top three cards. You may cast one of them without paying its mana cost.

Haste
Whenever Tunnel Moles attacks, you may have it phase out. (Treat it and anything attached to it as though they don't exist until its controller's next turn.)
Whenever Tunnel Moles phases in, it gets +2/+2 until end of turn and can't be blocked by creatures with flying this turn.

Mountains you control have “{T}: Add {R}{R}.”
[+1]: Exile the top card of your library. You may play that card until the end of your next turn.
[–2]: Conjure six cards named Scorch. Shuffle them and your hand into your library, then draw two cards.

Archive 5 (As this enters the battlefield, shuffle the top five cards of your main library into a new face up library. Sacrifice this after the archived library is empty.)
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.)
When you get your eighth research counter, exile Turin's Study, then you may cast any number of nonland cards from the archived library without paying their mana costs.

{1}{R}, Discard a card: Draw a card.
{R}: You may put a creature card from your hand onto the battlefield. That creature gains haste. Activate only if twenty or more cards are in your graveyard.

Exchange control of all creatures you and target player control until end of turn. Untap those creatures. They gain haste until end of turn.

Shimmer (Whenever this creature attacks, create a tapped and attacking token that's a copy of it. Exile the token at the beginning of the end step.)

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.)

Flying, menace, haste
Twisted Archangel has indestructible as long as an opponent has four or more cards in hand.

Whenever Twitchy Pyromancer enters or attacks, it deals 1 damage to any target. Whenever a creature dealt damage this way dies this turn, upgrade Twitchy Pyromancer. (Give it one of the listed counters it doesn't already have.)
• +1/+1
• Menace
• Prowess

At the beginning of your upkeep, exile the top card of your library. You may play it this turn. Whenever you cast an instant or sorcery spell exiled this way, you may copy it and you may choose new targets for the copy.

This spell costs {1} less to cast for each foretold card you own in exile, each permanent you control with foretell, and each card with foretell in your graveyard.
Flying
When Tyrant of Prophecies enters, it deals 3 damage to any target.

This spell costs {X} less to cast, where X is the power of the creature it targets.
Tyrant's Reckoning deals 4 damage to target creature.

Haste
Madness {3}{R} (If you discard this card, discard it into exile. When you do, cast it for its madness cost or put it into your graveyard.)

Flying
{1}{R}{R}{R}: Return Umbral Hunter from your graveyard to your hand. If it's the declare attackers step, up to one target attacking creature gets +3/+1 until end of turn.

Assault {X}{R}{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.)
Other Elementals you control get +1/+0.
When Unbound Annihilus assaults, create X 1/1 red Elemental creature tokens that are tapped and attacking.