msem-instigator

Tinyvale Treetops enters tapped unless you played it from exile.
{T}: Add {G} or {W}.

{T}: Add {C}.
{T}, Exile two cards from your graveyard: Add {R} or {W}.

{T}: Add {C}{C}. Spend this mana only to cast spells with mana value 5 or greater.

Tomb of Great Drakes enters tapped.
{T}: Add {U}.
{2/U}{2/U}: Tomb of Great Drakes becomes a 2/2 blue Elemental creature with flying until end of turn. It's still a land.

{T}: Add {C}.
{1}: Tomb of Shifting Sands becomes a copy of target land card in any graveyard, except it has this ability and it's a Desert in addition to its other types. (This effect lasts indefinitely.)

Tomb of the Roseblade enters tapped.
{T}: Add {C}.
{X}, {T}, Sacrifice Tomb of the Roseblade: Search your library for an Equipment card with mana value X or less, put it onto the battlefield, then shuffle. Activate only as a sorcery.

({T}: Add {U} or {R}.)
Torrid Geysers enters tapped unless you control two or more basic lands.

Torrid Path enters tapped unless you control one or fewer other lands.
{T}: Add {R} or {W}.
Cycling {2} ({2}, Discard this card: Draw a card.)

Enchant creature
Enchanted creature gets +3/+3 and has trample.

{T}: Add {C}.
{2}, {T}: Draw a card. Activate only if you have no cards in hand.

Vigilance, reach
When this creature transforms into Towering Alpha, return target card from your graveyard to your hand.
At the beginning of your end step, if Towering Alpha didn't attack this turn, transform it.

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.