msem-instigator

If it isn't an extra turn, take an extra turn after this one. (Cast a copy of this spell once while this creature is on the battlefield.)

When Grievous Buccaneer enters, it voyages. (If it isn't blocking or targeted by another spell or ability, it phases out.)
Whenever Grievous Buccaneer phases in, tap target creature an opponent controls. That creature doesn't untap during its controller's next untap step.

Griffin Country enters with a feather counter on it.
Creatures with flying you control get +1/+1.
{U}, Remove a feather counter from Griffin Country: Put a flying counter on target creature you control.
{2}{U}, Remove a feather counter from Griffin Country: Search your library for a creature card with flying, reveal it, put it into your hand, then shuffle.

Rapport — Whenever Grinning Fox and at least one other creature you control become tapped, tap another target creature. That creature doesn't untap during its controller's next untap step.

Put target creature on top of its owner's library.

Prowess
Grizzled Stoker can't be blocked as long as you control an artifact.

When Guardian of Lost Truths enters, if a library has twenty or fewer cards left in it, draw two cards. Otherwise, target player mills five cards.

At the beginning of your upkeep, draw a card, then discard a card.
{4}{U}: Tap target creature an opponent controls. It doesn't untap during its controller's next untap step.

When Gulchdrinker Serpent enters, detain target permanent. (Until your next turn, that permanent can't attack or block and its activated abilities can't be activated.)

When Gusma's Artisan enters, search your library for a card, then shuffle and put that card on the bottom of it.
{2}{U}, Sacrifice Gusma's Artisan: Manifest the bottom card of your library. (To manifest a card, put it onto the battlefield face down as a 2/2 creature. Turn it face up any time for its mana cost if it's a creature card.)

Prowess
Gusma's Emissary gets +1/+1 as long as you control a black or green permanent.

Flying
{1}{U}: Put Gustscreen Cherub on the bottom of its owner's library.
Morph {1}{U} (You may cast this card face down as a 2/2 creature for {3}. Turn it face up any time for its morph cost.)

Hafiq the Wise has hexproof as long as you've cast a spell this turn.
{U}, Discard a card with mana value X: Counter target spell with mana value X.
{U}, Sacrifice another permanent with mana value X: Return target instant or sorcery card with mana value X from your graveyard to your hand.

Whenever a Survivor you control enters, look at the top card of target opponent's library. You may have them put that card into their graveyard.

Flash
Enchant creature
Enchanted creature gets -3/-0 and doesn't untap during its controller's untap step.

When Hand of Dominion enters, tap target creature. It doesn't untap during its controller's next untap step.
At the beginning of your upkeep, if your fealty to Islands is five or greater, transform Hand of Dominion. (Each Island you control counts towards your fealty to Islands.)

Spirited (When this creature enters, you may activate one of its activated abilities without paying its cost.)
{U}, {T}: You may tap or untap target Human.

Vanishing 3 (This creature enters with three time counters on it. At the beginning of your upkeep, remove a time counter from it. When the last is removed, sacrifice it.)
When Hapless Chronomancer dies, if it had no time counters on it, return target instant or sorcery card from your graveyard to your hand.

Slipstream (This creature can't be blocked as long as only creatures with slipstream are attacking.)
Whenever Happy Manta deals combat damage to a player, draw a card for each card type among spells you've cast this turn.

{U}, Give yourself a lore counter: Scry 1. This ability costs {2} more to activate for each lore counter you have.
{6}{U}, Remove three lore counters from yourself, Sacrifice Harbinger of Giradrus: Draw seven cards, then create two 4/4 red Dragon creature tokens with flying.

When Hardlight Visionary enters, create a Function token with “Until end of turn, target creature becomes a 5/5 Dragon and gains flying.” (It's an enchantment. As you cast an instant or sorcery spell, sacrifice any number of Functions to add their effects to that spell.)

Draw two cards. Each opponent draws a card.

Target creature an opponent controls loses all abilities and has base power and toughness 0/1 until end of turn.
Showcase {4}{U} (Then if you cast this for its showcase cost, create a 1/1 red Bard creature token that can't block and exile this. Whenever it attacks, you may cast a free copy of this.)

Whenever you cast an instant or sorcery spell from your hand, put that card onto the battlefield face down as a 2/2 creature instead of putting it into your graveyard as it resolves.
Whenever a face-down creature you control deals combat damage to an opponent, you may exile it. If you do, you may cast it without paying its mana cost.

You may activate loyalty abilities of target planeswalker you control an additional time this turn.
Fabled {1}{U}{U} (Then if you cast this for its fabled cost, put it onto the battlefield transformed attached to that planeswalker.)