msem-instigator

(Choose only one work as a sorcery to add its ability.)
When Those Lost to the Waves enters, search your library for an artifact card with mana value 3 or less, reveal it, put it into your hand, then shuffle.
{1}{W}: Fight the Current
Equipped creatures you control get +1/+1.
{3}{U}: Soul of the Sea
At the beginning of combat on your turn, you may have target noncreature artifact become a 3/3 artifact creature until end of turn.

Counter target instant or sorcery spell. If that spell is countered this way, exile it instead of putting it into its owner's graveyard. You may cast that spell for as long as it remains exiled and you may spend blue and black mana as though it were mana of any color to cast it.

The next creature spell you cast this turn may be cast as though it had flash and costs {1} less to cast. If it entering the battlefield causes a triggered ability of it to trigger, that ability triggers an additional time.

Whenever a creature you control enters, Timid Thunderhorn gets +X/+X until end of turn, where X is that creature's power.

Each creature you control enters with an additional +1/+1 counter on it.
When Training Sim enters, create a Function token with “Target creature you control fights target creature you don't control.” (It's an enchantment. As you cast an instant or sorcery spell, sacrifice any number of Functions to add their effects to that spell.)

Whenever you cast an Aura spell, put two +1/+1 counters on Traveling Thespians.

Target player sacrifices a creature.
Inscribe {3}{B}{R} ({3}{B}{R}: Exile this card from your hand inscribed on a creature you control. Whenever that creature attacks, its controller may cast a copy of the inscribed card without paying its mana cost. Inscribe only as a sorcery.)

Equipped creature gets +1/+0 for each artifact you control.
As long as you control three or more artifacts, equipped creature has flying and haste.
Equip {3}

If you would put one or more counters on a creature you control or on yourself, put that many plus one of each of those kinds of counters on that creature or player instead.
{2}{G}{U}, Sacrifice Triton's Invocation: Draw cards equal to the greatest number of counters among creatures you control and yourself.

Flash
When Turned by Fear enters, return up to one target creature to its owner's hand.
At the beginning of combat on your turn, up to one target creature gains menace until end of turn.

When Twilight of the Intisuyu enters, draw a card, then choose a card name.
Permanents you control with the chosen name have lifelink and ward {1}.

Renown 1 (When this creature deals combat damage to a player, if it isn't renowned, put a +1/+1 counter on it and it becomes renowned.)
{4}{R}{G}: Twinblade Paragon gains double strike until end of turn.

{T}, Sacrifice a permanent: Investigate. (Create a colorless Clue artifact token with “{2}, Sacrifice this artifact: Draw a card.”)

When Undermarket Favors enters, target player discards a card, then mills four cards.
{1}, Sacrifice Undermarket Favors: Draw a card.

Prowess
Whenever Unseen Hand attacks, exile target noncreature, nonland card with mana value 1 or less from your graveyard. Copy that card. You may cast the copy. (You still pay its costs.)

Ward {1}
Other Scouts you control get +1/+1.
Whenever three or more Scouts you control attack, draw a card.

Rhapsody {4}{R}{W} (Pay {4}{R}{W} to cast this as a 4/4, or as a sorcery to make it become a 4/4.)
Lifelink, haste

You may have Urushi, the Ripple in the Smoke enter as a copy of any creature on the battlefield, except it's an enchantment. (It's not a creature.)

Enchant creature
When Valorous Ideal enters, target creature can't block this turn.
Enchanted creature gets +2/+0 and attacks each combat if able.
When Valorous Ideal is put into a graveyard from the battlefield, return Valorous Ideal to its owner's hand.

Counter target spell unless its controller pays {3}.

Choose one—
• Destroy target permanent with mana value 2.
• Return target permanent card from a graveyard to its owner's hand.
Exile Veil's Recovery.

Haste
Whenever you cast a noncreature spell, put a +1/+1 counter on Vengeant Precursor. It gains trample until end of turn.

(Add a quest counter as this enters. Sacrifice after 3.)
Whenever you cast an Equipment or Adventure spell, add a quest counter.
Exile the top two cards of your library, then choose one of them. You may play that card until the end of your next turn.
Until end of turn, target creature you control gets +1/+0 and gains double strike, vigilance, and indestructible.

Vision (Whenever this or another creature you control enters, reveal the top card of your library. Then you may put that card into your graveyard.)
Whenever Vessel of Lost Souls envisions a creature card, you may have it become a copy of that card until end of turn.

Deathtouch, protection from legendary
Vielle, Undercity Wayfarer has all loyalty abilities of permanents on the battlefield that cost +1, +0, or -1. (Before cost changes. Add or remove loyalty counters from Vielle to pay their loyalty costs.)