msem-instigator

Towering Boughs enters tapped.
{T}: Add {R} or {G}.
{3}{R}{G}: Until end of turn, Towering Boughs becomes a 6/6 red and green Treefolk creature with with trample and “Whenever this creature attacks or blocks, torment yourself.” It's still a land. (To torment yourself, lose 3 life unless you discard a card or sacrifice a nonland permanent.)

Toxic Jungle enters tapped unless you have 15 or less life.
{T}: Add {B} or {G}.

As Toxic Spring enters, you may tap an untapped creature you control. If you don't, Toxic Spring enters tapped.
{T}: Add {U} or {B}.

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.

Tranquil Cove enters tapped.
When Tranquil Cove enters, you gain 1 life.
{T}: Add {W} or {U}.

Tranquil Shrine enters tapped.
When Tranquil Shrine enters, if you don't control a legendary creature, sacrifice it unless you pay {1}.
{T}: Add one mana of any color.

({T}: Add {W} or {U}.)
Tranquil Stream enters tapped.

{T}: Add {C}.
{7}: Transplanted Citadel becomes a 6/6 Golem artifact creature until end of turn. It's still a land. This ability costs {1} less to activate for each artifact you control.

Treacherous Den enters tapped.
{T}: Add {B} or {R}.
{2}{B}{R}, {T}, Sacrifice Treacherous Den: Draw a card.

Treacherous Oasis enters tapped.
{T}: Add {U} or {B}.
{2}{U}{B}: Until end of turn, Treacherous Oasis becomes a Crocodile creature in addition to its other types. It can't be blocked this turn.
Scavenge {1}{U}{B}

{T}: Add {C}.
{3}, {T}, Sacrifice Treasure Beach: Create three Treasure tokens. (They have “{T}, Sacrifice this artifact: Add one mana of any color.”)

As Tree of Timelines enters, you may pay 3 life. If you don't, it enters tapped.
{T}: Add {B}, {G}, or {U}.

{T}, Pay 1 life: Add {G}.
{T}, Pay 1 life, Sacrifice Tropical Grove: Search your library for a Forest card, put it onto the battlefield tapped, then shuffle.

(Transform this if it's not attached to a creature. Pay {2}{W} as a sorcery to unattach it.)
Enchant creature you control
Trusty Steed's rider gets +2/+2.

Tsubasa's Redoubt enters tapped.
When Tsubasa's Redoubt enters, you may mill two cards.
{T}: Add {W} or {B}.

Hexproof
Whenever this creature transforms into Tsunami Titan or attacks, you may return target creature to its owner's hand.

Twisting Fissure enters tapped.
{T}: Add {U} or {R}.
{1}, {T}: Add one mana of any color.

You may play Typhoon Caverns from your graveyard as long as seven or more cards are in your graveyard.
Typhoon Caverns enters tapped.
{T}: Add {U} or {B}.
Cycling {1}{U}{B} ({1}{U}{B}, Discard this card: Draw a card.)

Trample, haste
When Tyrants of Bundan enters, tap all lands target player controls. They don't untap during their controller's next untap step.

{T}: Add {C}.
{3}{B}: Until end of turn, Tzhai's Throne becomes a 2/2 creature. It's still a land. It gets +2/+2 if {R} was spent to activate this ability, gets +2/+2 if {G} was spent, and gets +2/+2 if {W} was spent.

Unbound Spirit can't be blocked.
When you attain Unbound Spirit, tap target creature. That creature doesn't untap during its controller's next untap step.

Uncharted Haven enters tapped.
As Uncharted Haven enters, choose a color.
{T}: Add one mana of the chosen color.

Enchant creature
Enchanted creature has first strike. (That creature deals combat damage before creatures without first strike.)

Flying, vigilance
When you attain Unfallen Angel, target opponent discards a card.

Unfettered Noble can't be blocked unless defending player pays 3 life, discards a card, or sacrifices a nonland permanent for each creature they control that's blocking it.
Sacrifice a nonland permanent: Unfettered Noble gains indestructible until end of turn.