msem-instigator

Whenever Drownyard Colossus or another creature you control enters, any number of target players each mill cards equal to that creature's toughness.
{2}{U}{B}, {T}: Draw a card, then create a 0/3 blue Crab creature token with “{T}: Target player mills a card.”

Reach

Whenever Dryad of Rippling Leaves enters or you draw a card except during your draw step, scry 1. (To scry 1, look at the top card of your library. You may put that card on the bottom of your library.)

Haste
Ward—Pay 3 life.
{R}, Tap an untapped artifact you control: Drysand Mole gets +1/+0 until end of turn. Up to one target creature can't block it this turn.

{2}: Duela Duelist gains first strike until end of turn.
{3}: Duela Duelist gains distorted until end of turn. (This creature can be blocked by tapped creatures but not untapped creatures.)

First strike, menace
Whenever Dueling Duo or another creature you control becomes blocked, that creature deals 1 damage to each creature blocking it.

As Duke Gerard Hoff enters, an opponent gains control of it.
Duke Gerard Hoff can't attack its owner or planeswalkers that player controls.
Creatures your opponents control get +2/+1.

{3}{R}: Target creature can't be blocked this turn if it's an artifact creature or has power 2 or less.

{T}, Sacrifice an artifact or creature: Each opponent loses 1 life and you gain 1 life.

When Duncaster Nightwatcher enters and whenever you cast a noncreature spell, create a 1/1 colorless Human creature token.
Whenever you attack with three or more creatures, return target noncreature, nonland card with mana value 3 or less from your graveyard to your hand.

Whenever you scry, put a +1/+1 counter on Dunesea Cartographer for each card you looked at while scrying this way.
{3}{W}{U}: Scry 2.

Flash
When Duplicated Dismantler enters, if you cast another spell this turn, return target spell to its owner's hand.

Lifelink
{W}{B}, {T}: Dusk Rider deals X damage to target attacking creature, where X is the number of Spirits you control.

Landfall — Whenever a land you control enters, target creature you control gains vigilance until end of turn.

Each other nontoken Elf and/or Warrior you control enters with an additional +1/+1 counter on it.
{G}{G}, {T}, Remove two +1/+1 counters from among creatures you control: Create two 1/1 green Elf Warrior creature tokens.

Dutiful Chasqui gets +2/+1 as long as you control two or more other creatures that share a name with it.
A deck can have any number of cards named Dutiful Chasqui.

When Dutiful Counselor enters, adjudicate. (Create a white Aura enchantment token with enchant creature and “Sacrifice this token: Untap enchanted creature” attached to target creature.)
Whenever an Aura you control enters, you may pay {1}. If you do, target creature gets +1/+1 until end of turn.

First strike (This creature deals combat damage before creatures without first strike.)

{4}{G}{G}: Eager Voyager voyages. (If it isn't blocking or targeted by another spell or ability, it phases out.)
Whenever Eager Voyager phases in, if it has no +1/+1 counters on it, put four +1/+1 counters on it.

First strike
{1}{R}, Discard a card: East Ward Forgetender gets +2/+0 until end of turn.

Flying, haste
Whenever Eavesknocker attacks, another target attacking creature gets +1/+1 until end of turn.

Prowess
Vanishing 2 (This creature enters with two time counters on it. At the beginning of your upkeep, remove a time counter from it. When the last is removed, sacrifice it.)

Distorted (This creature can be blocked by tapped creatures but not untapped creatures.)
{1}{W}: Target creature and all creatures with the same name as that creature get +0/+1 until end of turn.