msem-instigator

Each player discards their hand, then draws cards equal to the greatest number of cards discarded this way.

Haunted Estate enters the battlefield tapped unless another player controls a land that could produce {W} or {B}.
{T}: Add {W} or {B}.

{W}: Target creature assigns combat damage equal to its toughness rather than its power this turn.

Whenever you cast a black spell, you may exile target creature. Return that card to the battlefield under its owner's control at the beginning of the next end step.
Whenever you cast a red spell, you may have Haunted Sunseeker deal 1 damage to each creature.

{W}, Sacrifice Haunting Bard: Destroy target artifact or enchantment.

Lifelink
Whenever you sacrifice a creature, you gain life equal to its power.

Flying
Whenever Haunting Horseman deals combat damage to a player, that player discards a card.

Flying, lifelink

Put target creature on top of its owner's library.
Quickdraw {2}{U} (When a creature you control blocks or becomes blocked, you may cast this spell for {2}{U}.)

Menace
When Heart of the Deadwood enters the battlefield, destroy up to one target creature, then put up to one target creature card from a graveyard onto the battlefield under your control.

Reach

Enchant creature
Prevent all damage that would be dealt by enchanted creature.
{R}, Sacrifice Heat of Day: It deals 2 damage to enchanted creature.

Until end of turn, gain control of target creature and it gains haste and shimmer. Untap it. (Whenever it attacks this turn, create a tapped and attacking token that's a copy of it. Exile that token at the beginning of the end step.)

{1}, {T}: Add one mana of any color.
{1}, {T}, Sacrifice Heavy Moneybag: Post a bounty on target creature or planeswalker. Activate only as a sorcery. (Put a bounty counter on that creature. It has “When this creature dies, each opponent draws a card” as long as it has a bounty counter on it.)

[+1]: Tap target nonland permanent. It doesn't untap during its controller's next untap step.
[–2]: Exile target tapped nonland permanent.
[–4]: Target player skips their next untap step. Tap up to three target permanents.

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

{6}: Until the next time this ability resolves, and as long as Helm of the Infinite and target creature you control are on the battlefield, each other creature is a copy of that creature, and effects that would cause permanents to become creatures cause them to become copies of that creature instead.

(As this Saga enters and after your draw step, add a lore counter. Sacrifice after III.)
I, II — Put a +1/+1 counter on target creature you control. It gains vigilance until end of turn.
III — Target creature you control gets +2/+2 and gains flying, vigilance, and lifelink until end of turn.
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{1}{U}, {T}: Reveal the top card of your library. If it doesn't share a color with Heretical Seer, put it into your hand.

For each color among nontoken permanents you control, add one mana of that color.

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

Target creature gains flying and gets +1/+0 for each card in your hand until end of turn.
Fuse (You may cast one or both halves of this card from your hand.)

Flying
When High Spirits enters the battlefield, target creature gains flying until end of turn.

When Hired Kalak enters the battlefield, put target card from your graveyard on top of your library.

Flying
Whenever a Harpy you control becomes the target of a spell, scry 1.