msem-instigator

Whenever Leyline Tracer attacks, exile the top card of your library. Until end of turn, you may play that card.
Ascend—{B}, Discard two cards. ({B}, Discard two cards: Exile this creature, then return it to the battlefield transformed. Ascend only as a sorcery.)

When Leyran Spellchainer enters, return target instant or sorcery card from your graveyard to your hand.
{2}{R}: Transform Leyran Spellchainer. Activate only if it's attacking.

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.)
Lha Elite's power is equal to the number of tokens you control.

Trample
Lian Taizi gets +1/+1 for each card in your hand.
When Lian Taizi enters, return any number of target cards with different mana values from your graveyard to your hand.

Lifelink
If a creature or planeswalker would die, instead exile it and put a +1/+1 counter on Librarian of Whispers.

Menace
Whenever Lieshi Pariah deals combat damage, you lose that much life unless it's in a pack. (Two or more creatures you control with equal power are in a pack.)

When Life's Harbinger dies, you may put a +1/+1 counter on target creature you control.
{T}: Add {G}.

Whenever a +1/+1 counter is put on Lifeblood Leecher, target creature an opponent controls gets -1/-1 until end of turn.

{3}{G}: Put a +1/+1 counter on Lifecaller Dryad.

When Lifespark Alchemist enters, create a Vial token. (It's an artifact with “{1}, Sacrifice this and another permanent: Draw a card. Activate only during your turn.”)
Whenever Lifespark Alchemist or another creature dies, each opponent loses 1 life.

Distorted (This creature can be blocked by tapped creatures but not untapped creatures.)

Whenever you activate a loyalty ability of a planeswalker, you gain 1 life.

Haste
At the beginning of each end step, if Lightning Ox dealt damage this turn, sacrifice it.

Whenever another artifact you control enters, put a +1/+1 counter on Lightsteel Enforcer.

Lightwalker has flying as long as it has a +1/+1 counter on it.

When Lilyreed Triton enters, create a white Aura enchantment token named Triton's Gift attached to target creature. The token has enchant creature and “Enchanted creature gets +1/+0 and can't be blocked by creatures with power 3 or greater.”

When Lisa, the Daughter enters, create Mother, a legendary 4/1 black Demon creature token with flying and “This creature can't block.”
If a source would deal damage to Lisa while you control a Demon creature, instead that damage is dealt to a Demon creature you control of your choice.

Whenever you gain life, put a +1/+1 counter on Listless Maneli.
Surpass {5}{W} ({5}{W}: Transform this creature. This costs {1} less to activate for each counter on it. Activate only as a sorcery.)

Whenever Little Kibo attacks, you may pay {W}{W}. If you do, transform it.

When Little Pig enters, if you control a land named Far-Off Lands, put two +1/+1 counters on it.

Living Broadcast can't block.
Whenever you cast a spell from exile, you may return Living Broadcast from your graveyard to your hand.

{2}{B}, Exile Lizhao's Soulblade from your graveyard: Return target creature card from your graveyard to your hand. Activate only as a sorcery.

Each other creature you control that's an Elf or a Warrior gets +1/+1.
{2}, Sacrifice Llanowar Exemplar: Creatures you control gain indestructible until end of turn.

When this creature enters, create a Treasure token.
This creature gets +1/+1 for each different name among tokens you control.