Council's Judgment

Will of the council — Starting with you, each player votes for a nonland permanent you don't control. Exile each permanent with the most votes or tied for most votes.

Fall of the Impostor

(As this Saga enters and after your draw step, add a lore counter. Sacrifice after III.)
I, II — Put a +1/+1 counter on up to one target creature.
III — Exile a creature with the greatest power among creatures target opponent controls.

Venture Forth

Exile cards from the top of your library until you exile a land card. Put that card onto the battlefield and the rest on the bottom of your library in a random order. Exile Venture Forth with three time counters on it.
Suspend 3—{1}{G}

Fear of Impostors

Flash
When this creature enters, counter target spell. Its controller manifests dread. (That player looks at the top two cards of their library, then puts one onto the battlefield face down as a 2/2 creature and the other into their graveyard. If it's a creature card, it can be turned face up any time for its mana cost.)

Council's Deliberation

Draw a card.
Whenever you scry, if you control an Island, you may exile this card from your graveyard. If you do, draw a card.

Confirm Suspicions

Counter target spell.
Investigate three times. (To investigate, create a Clue token. It's an artifact with "{2}, Sacrifice this token: Draw a card.")

Illicit Masquerade

Flash
When this enchantment enters, put an impostor counter on each creature you control.
Whenever a creature you control with an impostor counter on it dies, exile it. Return up to one other target creature card from your graveyard to the battlefield.

Dark Impostor

{4}{B}{B}: Exile target creature and put a +1/+1 counter on this creature.
This creature has all activated abilities of all creature cards exiled with it.

Vent Sentinel

Defender
{1}{R}, {T}: This creature deals damage to target player or planeswalker equal to the number of creatures you control with defender.

Faerie Impostor

Flying
When this creature enters, sacrifice it unless you return another creature you control to its owner's hand.

A Killer Among Us

When this enchantment enters, create a 1/1 white Human creature token, a 1/1 blue Merfolk creature token, and a 1/1 red Goblin creature token. Then secretly choose Human, Merfolk, or Goblin.
Sacrifice this enchantment, Reveal the creature type you chose: If target attacking creature token is the chosen type, put three +1/+1 counters on it and it gains deathtouch until end of turn.

Sakashima the Impostor

You may have Sakashima the Impostor enter as a copy of any creature on the battlefield, except its name is Sakashima the Impostor, it's legendary in addition to its other types, and it has "{2}{U}{U}: Return Sakashima the Impostor to its owner's hand at the beginning of the next end step."

Vote Out

Convoke (Your creatures can help cast this spell. Each creature you tap while casting this spell pays for {1} or one mana of that creature's color.)
Destroy target creature.