msem-instigator

Exchange control of all creatures you and target player control until end of turn. Untap those creatures. They gain haste until end of turn.

Each creature you control with a +1/+1 counter on it has double strike.
If one or more +1/+1 counters would be put on a creature you control, put that many plus one +1/+1 counters on that creature instead.

Choose one—
• Scry 3. Draw a card.
• Fateseal 3. That player draws a card. (To fateseal 3, look at the top three cards of an opponent's library, then put any number of them on the bottom of that player's library and the rest on top in any order.)

Flying, menace, haste
Twisted Archangel has indestructible as long as an opponent has four or more cards in hand.

Search your library and/or graveyard for a creature card with mana value X or less and put it onto the battlefield with an additional -1/-1 counter on it. If you search your library this way, shuffle.

Create four 3/3 green Elemental creature tokens.
Flashback {7}{G}{G}{G} (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Cast this spell only if you have 10 or less life.
Flying, trample

At the beginning of your upkeep, exile the top card of your library. You may play it this turn. Whenever you cast an instant or sorcery spell exiled this way, you may copy it and you may choose new targets for the copy.

This spell costs {1} less to cast for each foretold card you own in exile, each permanent you control with foretell, and each card with foretell in your graveyard.
Flying
When Tyrant of Prophecies enters the battlefield, it deals 3 damage to any target.

Tyrant of the Depths has hexproof as long as it's untapped.
Whenever you cycle Tyrant of the Depths or it attacks, tap target nonland permanent you don't control and put a stun counter on it.
Basic landcycling {1}{U} ({1}{U}, Discard this card: Search your library for a basic land card, reveal it, and put it into your hand, then shuffle.)

Flying, vigilance
When Tyriel, Angelic Artisan enters the battlefield, you may search your library for an Equipment card, reveal it, put it into your hand, then shuffle.
Whenever Tyriel attacks, you may put an Equipment card from your hand onto the battlefield, then attach it to Tyriel.

Whenever Ujuraq, Elder Watcher enters the battlefield or attacks, surveil 1. (Look at the top card of your library. You may put that card into your graveyard.)
Ujuraq gets +3/+3 and has trample as long as there are eight or more cards in your graveyard.

Vision (Whenever this or another creature enters the battlefield under your control, reveal the top card of your library. Then you may put that card into your graveyard.)
Whenever Ulek Crusher envisions a creature card, it gets +2/+2 until end of turn.

Cast this spell only if you control a creature.
Exile all creatures.

{2/B}: Umbral Stalker gains indestructible until end of turn. Tap it.

Resolute — Umbral Wolf can't be blocked by more than one creature as long as Umbral Wolf's power is greater than its base power.

Assault {X}{R}{R} (Whenever this attacks, if it has no +1/+1 counters on it, you may pay its assault cost to put a +1/+1 counter on it.)
Other Elementals you control get +1/+0.
When Unbound Annihilus assaults, create X 1/1 red Elemental creature tokens that are tapped and attacking.

Whenever you cast another creature spell, create a 1/1 green and white Elk Spirit creature token.
As long as you control five or more Elk, creatures you control get +3/+3 and have trample.

Target opponent sacrifices half the permanents they control, rounded down.

Search your library for a permanent card with mana value X or less, reveal it, put it into your hand, then shuffle.

Hexproof
When Uncharted Leviathan enters the battlefield, target creature can't be blocked this turn.

When Uncovered Secrets enters the battlefield, search your library for an artifact card, reveal that card, then shuffle and put that card on top.
Concord — Creatures you control get +1/+1 as long as there are four or more card types among permanents you control.

When Undead Archivist enters the battlefield, return target instant or sorcery card from your graveyard to your hand.
Revive {5}{U} ({5}{U}, 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.)

Creature cards in your graveyard have revive {2}{B}{B}. ({2}{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.)

You may have Undecided Mimic enter the battlefield or phase in as a copy of any creature on the battlefield, except it has this ability and “{2}{U}{U}: Undecided Mimic phases out.” (Treat it and anything attached to it as though they don't exist until its controller's next turn.)