msem-instigator

Target player sacrifices an attacking or blocking creature.

As Aquatic Refuge enters, you may tap an untapped creature you control. If you don't, Aquatic Refuge enters tapped.
{T}: Add {W} or {U}.

Flying, haste
Prowess (Whenever you cast a noncreature spell, this creature gets +1/+1 until end of turn.)

[+1]: Each opponent loses 1 life and you gain 1 life. Mill a card. If you do, you may shuffle a card from your graveyard into your library.
[0]: Any number of target players each discard a card. If you have an insight counter, return up to one creature card from your graveyard to your hand.
[0]: You get an insight counter.
[–2]: Target creature gets -3/-3 until end of turn.

Whenever you cast your second spell each turn, you may tap target creature and put a stun counter on it.

Flying, vigilance
When Warden of Seas enters, tap all other creatures.
Each opponent can't untap more than one nonland permanent during each of their untap steps.

Haste
Whenever Emblazoned Qilin attacks, it gains flying until end of turn if it's in a pack. (Two or more creatures you control with equal power are in a pack.)

You may cast spells as though they had flash.

Destroy target creature. Search your library for a basic land card, put it onto the battlefield tapped, then shuffle.

Pyrostorm deals 10 damage divided as you choose among any number of targets.

Whenever Bloodthirsty Insurgent attacks, it gets +2/+0 until end of turn.

You may pay {U} and tap an untapped Rogue you control rather than pay this spell's mana cost.
Counter target spell unless its controller pays {2}.

Elf creatures you control get +2/+2 and gain trample until end of turn.
Elfcycling {2}{G} ({2}{G}, Discard this card: Search your library for an Elf card, reveal it, and put it into your hand, then shuffle.)

Mark (Whenever this creature attacks, mark target creature until end of turn.)
Whenever a marked creature an opponent controls dies, create a Food token. (It's an artifact with “{2}, {T}, Sacrifice this artifact: You gain 3 life.”)

At the beginning of your end step, amass Soldiers 1. (Put a +1/+1 counter on an Army you control. It's also a Soldier. If you don't control one, create an 0/0 black Soldier Army creature token first.)

Whenever Loyalist Escort or another Knight or Soldier you control enters, you may choose one that hasn't been chosen this turn —
• Tap target creature an opponent controls.
• Untap target creature you control.

Experience (Whenever this creature attacks, if it has fewer than three +1/+1 counters on it, put a +1/+1 counter on it.)
Whenever a +1/+1 counter is put on Treecrawler Elemental, you may have it fight target creature. (Each deals damage equal to its power to the other.)

Equipped creature gets +1/+1.
Whenever equipped creature deals combat damage to a player, Ornamental Longbow deals 1 damage to any target.
Equip {2}

At the beginning of your upkeep, create an Idol token. (It's an artifact with “{1}, Sacrifice this artifact: Put a +1/+1 counter on target creature. Activate only as a sorcery.”)
{5}{W}{W}, Sacrifice three Idols: Return target creature card from your graveyard to the battlefield with three +1/+1 counters on it.

As Harlowe, Thespian Extraordinaire enters, choose a color and creature type.
Harlowe, Thespian Extraordinaire is the chosen color.
Harlowe, Thespian Extraordinaire is the chosen type in addition to its other types.

Archive 5 (As this enters, shuffle the top five cards of your main library into a new face up library. Sacrifice this after the archived library is empty.)
Whenever you draw a card from another one of your libraries, you draw a card from the archived library and you lose 1 life.

[+2]: You may draw a card. If you don't, create a Treasure token. Repeat this process once.
[0]: Iviana deals X damage to each creature you don't control, where X is 2 plus twice the number of Dragons you control.
[–3]: Create a 5/5 red Dragon creature token with flying and haste.

Vanguard — Whenever a creature you control attacks alone, it gets +1/+3 until end of turn.

Deathtouch
{3}{G}: Deathcoil Cobra gains indestructible until end of turn.

Enchant opponent
Cards in enchanted player's graveyard lose all abilities and all names.
If enchanted player would mill one or more cards, they instead mill that many cards plus X, where X is the number of Curses attached to them.