msem-instigator

(As this Saga enters and after your draw step, add a lore counter. Sacrifice after III.)
I — Return target creature card from your graveyard to your hand.
II — Return target instant or sorcery card from your graveyard to your hand.
III — At the beginning of the next end step, create an X/X black Horror creature token, where X is the number of spells you cast this turn.

When The Raven Queen of Fretport enters, put a -1/-1 counter on each of any number of target creatures.
{2}{U}{B}: Proliferate. (Choose any number of permanents and/or players with counters on them, then give each another counter of each kind already there.)

Target player mills five cards. Draw a card for each card type among cards milled this way. (The card types are artifact, creature, enchantment, land, instant, planeswalker, sorcery, and tribal.)

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.

Whenever a creature enters under an opponent's control, draw a card unless that player pays {1}.

When Thoughtgrinder enters, each player discards a card.
Unearth {1}{U}{B} ({1}{U}{B}: Return this card from your graveyard to the battlefield. It gains haste. Exile it at the beginning of the end step or if it would leave the battlefield. Unearth only as a sorcery.)

{3}, Sacrifice Titanic Fossil: Mill three cards, then you may exile a card from your graveyard. You may cast a copy of the exiled card without paying its mana cost if the spell's mana value is 3 or less. Activate only as a sorcery.
{3}{U}{B}: Return Titanic Fossil from your graveyard to the battlefield transformed. Activate only during your turn.

Whenever Toxic Miscreant deals combat damage to a player, that player discards a card.

As Toxic Spring enters, you may tap an untapped creature you control. If you don't, Toxic Spring enters tapped.
{T}: Add {U} or {B}.

Choose a nonland card name. Search target player's graveyard, hand, and library for any number of cards with that name and exile them. That player shuffles. For each card exiled from their hand this way, you discard a card.

Treacherous Oasis enters tapped.
{T}: Add {U} or {B}.
{2}{U}{B}: Until end of turn, Treacherous Oasis becomes a Crocodile creature in addition to its other types. It can't be blocked this turn.
Scavenge {1}{U}{B}

Whenever an opponent casts their first spell each turn, that player may pay {1}. If they don't, you may create a Treasure token and you may draw a card.

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.

Flash
When Twisted Speaker enters, return target spell to its owner's hand. That spell's controller loses 2 life.

Whenever one or more cards are put into an opponent's graveyard from their hand or library, you may exile the top card of each player's library. Until your next turn, you may cast a card from among those exiled cards and you may spend mana as though it were mana of any type to cast that spell.

You may play Typhoon Caverns from your graveyard as long as seven or more cards are in your graveyard.
Typhoon Caverns enters tapped.
{T}: Add {U} or {B}.
Cycling {1}{U}{B} ({1}{U}{B}, Discard this card: Draw a card.)

{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.

Unearthed Legion's power and toughness are each equal to the number of cards in your graveyard.
At the beginning of your upkeep, mill a card.

Return target creature card from your graveyard to the battlefield, then search target opponent's library for a creature card and put that card onto the battlefield under your control. Then that player shuffles.

{T}, Pay 1 life: Add {U} or {B}.
{1}, {T}, Sacrifice Unlit Alley: Investigate. (Create a colorless Clue artifact token with “{2}, Sacrifice this artifact: Draw a card.”)

Whenever Vedlinn Ross becomes tapped, exile a nonland card from target opponent's graveyard. Copy it. You may cast the copy this turn. (You still pay its costs, including color. Copies of permanents enter as tokens.)
Whenever you cast a spell from anywhere other than your hand, copy it. You may choose new targets for the copies.

Whenever you cast a noncreature spell, torment each opponent. (They lose 3 life unless they discard a card or sacrifice a nonland permanent.)
{3}{U/B}{U/B}: Draw a card for each opponent with ten or more cards in their graveyard. You lose that much life.

{1}{U}{B}, Exile a creature card from your graveyard: Vestige of Evil has base power and toughness equal to the exiled creature's power and toughness 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.)