msem-instigator

When Lively Prop dies, look at the top three cards of your library. You may reveal a creature card from among them and put it into your hand. Put the rest into your graveyard.

Haste
Whenever Living Library attacks, you may draw a card. If you do, discard a card.

Whenever you draw a card, Living Script gets +1/+1 until end of turn.

Whenever Lone Freelancer becomes blocked, it deals damage equal to its power to defending player.

When Long Lost Cause enters, each opponent exiles a card from their hand or a creature they control.

Prowess
Whenever you cast a noncreature spell, noncreature spells you cast cost {1} less to cast until end of turn.

Flying (This creature can't be blocked except by creatures with flying or reach.)
When Lord of Swarms enters or dies, target creature gets -2/-2 until end of turn.

Other Merfolk you control get +1/+1.
{1}{U}: Target Merfolk gains slipstream until end of turn. (Creatures with slipstream can't be blocked as long as only creatures with slipstream are attacking.)

When Loresprout enters, if you control another creature, draw a card.

{2}{G}: Loreweaver's base power and toughness each become equal to the number of cards in your graveyard until end of turn.

Lost Explorer has first strike as long as it's attacking.
{1}{B}, Exile Lost Explorer from your graveyard: Crystallize. (Put a +1/+1 counter on a creature you control or create a Treasure.)

First strike, haste
Whenever Lothaire attacks, create a 0/0 colorless Reflection creature token that's tapped and attacking. Creatures you control get +1/+1 until end of turn.
{2}{R}{W}: Put a +1/+1 counter on each creature you control.

{T}, Mill a card: Add {B} or {G}.
Once each turn, when a creature you control dies or a creature card is put into your graveyard from anywhere other than the battlefield, each opponent loses 1 life.

When Lotus-Scarred Luocha enters, create a 2/1 black Spirit creature token with “This creature can't block.”
Whenever a creature in Lotus-Scarred Luocha's pack dies, each opponent loses 2 life and you gain 2 life. (Two or more creatures you control with equal power are in a pack.)

Trample
Lotusleaf Blade gets +1/+1 as long as you control another Warrior.

Motivate 2 (When this creature enters, you may motivate target creature with less power than this by putting two +1/+1 counters on it.)
Whenever a creature you control becomes motivated, you gain 2 life.

Ride {2}{W} ({2}{W}: Transform this and attach it to target creature you control without a Steed. Ride only as a sorcery.)

When Lumenbay Jailer enters, you may exile target nonartifact creature until Lumenbay Jailer leaves the battlefield.

Changeling (This card is every creature type.)
{1}: Another target creature you control gains the creature type of your choice until end of turn.
{1}: Change the text of another target creature you control by replacing all instances of one creature type with the creature type of your choice until end of turn.

When Lunar Defractor enters, each player discards a card.
Revive {5}{B}{B} ({5}{B}{B}, Exile this card from your graveyard: Create a token that's a copy of it except it has no mana cost. Revive only as a sorcery.)

Whenever you cast your first creature spell each turn, you may pay {1}. If you do, create a 1/1 colorless Spirit creature token.

Whenever one or more creatures in Luocha Mentor's pack attack, each creature in its pack gets +1/+0 until end of turn. (Two or more creatures you control with equal power are in a pack.)

Alpha (You may have this creature enter with a +1/+1 counter on it. If you do, it becomes alpha and can only attack alone.)
Hexproof

When Lysander Jal enters, create a token that's a copy of another target noncreature permanent you control.
Whenever you cast a spell from your graveyard, return target permanent card from your graveyard to your hand.

Attacking Pirates and Rogues you control get +1/+0.
{2}{U}: Tap target creature an opponent controls.