Lavinia, Foil to Conspiracy

Vigilance
Whenever you cast your second spell each turn, investigate. (Create a Clue token. It's an artifact with "{2}, Sacrifice this artifact: Draw a card.")
{T}: Add {C}{C}. Activate only during an opponent's turn.

Scuttling Sentinel

Flash
Vigilance
When Scuttling Sentinel enters, put a +1/+1 counter on another target creature you control. Until end of turn, that creature becomes a blue Crab in addition to its other types and gains hexproof. (It can't be the target of spells or abilities your opponents control.)

Lonis, Genetics Expert

Evolve (Whenever a creature you control enters, if that creature has greater power or toughness than this creature, put a +1/+1 counter on this creature.)
Whenever one or more +1/+1 counters are put on Lonis, investigate that many times.
Whenever you sacrifice a Clue, put a +1/+1 counter on another target creature you control.

Undercover Butler

Whenever Undercover Butler attacks the player with the most life or tied for most life, it can't be blocked this turn.

Resonance Technician

Flying
When Resonance Technician enters, you may discard a card. If you do, investigate twice.
{T}, Tap X untapped artifacts you control: Copy target instant or sorcery spell you control with mana value X. You may choose new targets for the copy.

Afterlife Insurance

Creatures you control gain afterlife 1 until end of turn. Draw a card. (When a creature with afterlife 1 dies, create a 1/1 white and black Spirit creature token with flying.)

Conclave Evangelist

Myriad (Whenever this creature attacks, for each opponent other than defending player, you may create a token copy that's tapped and attacking that player or a planeswalker they control. Exile the tokens at end of combat.)
Whenever Conclave Evangelist deals combat damage to a player, create a token that's a copy of Conclave Evangelist.

Sumala Rumblers

Sumala Rumblers's power is equal to the number of creatures you control.
Myriad (Whenever this creature attacks, for each opponent other than defending player, you may create a token copy that's tapped and attacking that player or a planeswalker they control. Exile the tokens at end of combat.)

Suppressor Skyguard

Flying
Whenever a player attacks you, if that player has another opponent who isn't being attacked, prevent all combat damage that would be dealt to you this combat.

Vernal Sovereign

Whenever Vernal Sovereign enters or attacks, create a green and white Elemental creature token with "This creature's power and toughness are each equal to the number of creatures you control."

Ordruun Mentor

Mentor (Whenever this creature attacks, put a +1/+1 counter on target attacking creature with lesser power.)
Whenever you attack a player, target creature that's attacking that player gains first strike until end of turn.

Memory Vampire

Flying
Whenever Memory Vampire deals combat damage to a player, any number of target players each mill that many cards. Then you may collect evidence 9. When you do, you may cast target nonland card from defending player's graveyard without paying its mana cost.

Dimir Strandcatcher

Flying
Whenever you attack, surveil X, where X is the number of opponents being attacked.
At the beginning of each end step, if three or more cards were put into your graveyard from anywhere other than the battlefield this turn, draw a card.

Tribune of Rot

Whenever Tribune of Rot attacks, mill two cards. For each creature card milled this way, create a 1/1 green Saproling creature token.

Boros Strike-Captain

Battalion — Whenever Boros Strike-Captain and at least two other creatures attack, exile the top card of your library. During any turn you attacked with three or more creatures, you may play that card.

Portal Manipulator

Flash
When Portal Manipulator enters during the declare attackers step, choose target player and any number of target attacking creatures their opponents control. Those creatures are now attacking that player.

Syndicate Heavy

Extort (Whenever you cast a spell, you may pay {W/B}. If you do, each opponent loses 1 life and you gain that much life.)
At the beginning of each end step, if you gained 4 or more life this turn, investigate. (Create a Clue token. It's an artifact with "{2}, Sacrifice this artifact: Draw a card.")

Amzu, Swarm's Hunger

Flying, menace
Other Insects you control have menace.
Whenever one or more cards leave your graveyard, you may create a 1/1 black and green Insect creature token, then put a number of +1/+1 counters on it equal to the greatest mana value among those cards. Do this only once each turn.

Corporeal Projection

Target creature you control gains myriad until end of turn. (Whenever it attacks, for each opponent other than defending player, you may create a token copy that's tapped and attacking that player or a planeswalker they control. Exile the tokens at end of combat.)
Overload {3}{U}{U}{R}{R} (You may cast this spell for its overload cost. If you do, change "target" in its text to "each.")

Carnage Interpreter

When Carnage Interpreter enters, discard your hand, then investigate four times. (To investigate, create a Clue token. It's an artifact with "{2}, Sacrifice this artifact: Draw a card.")
As long as you have one or fewer cards in hand, Carnage Interpreter gets +2/+2 and has menace.

Unruly Krasis

Trample
Whenever Unruly Krasis attacks, you may have the base power and toughness of another target creature you control become X/X until end of turn, where X is Unruly Krasis's power.
{3}{G}{U}: Adapt 3. (If this creature has no +1/+1 counters on it, put three +1/+1 counters on it.)

Stampede Surfer

Haste
Whenever Stampede Surfer attacks, for each opponent, you create a 2/2 green Boar creature token that's tapped and attacking that opponent.

Ecstatic Electromancer

Prowess (Whenever you cast a noncreature spell, this creature gets +1/+1 until end of turn.)
Whenever Ecstatic Electromancer enters or attacks, you may discard a card. If you do, draw a card.

Furious Spinesplitter

Trample
At the beginning of your end step, put a +1/+1 counter on Furious Spinesplitter for each opponent who was dealt damage this turn.

Aegis of the Legion

Equipped creature gets +1/+1 and has mentor. (Whenever it attacks, put a +1/+1 counter on target attacking creature with lesser power.)
Whenever equipped creature mentors a creature, put a shield counter on that creature. (If that creature would be dealt damage or destroyed, remove a shield counter from it instead.)
Equip {3}

Herald of Ilharg

Trample
Whenever you cast a creature spell, put two +1/+1 counters on Herald of Ilharg. If that spell has mana value 5 or greater, Herald of Ilharg deals damage equal to the number of counters on it to each opponent.

Frenzied Gorespawn

When Frenzied Gorespawn enters, for each opponent, goad target creature that player controls. (Until your next turn, those creatures attack each combat if able and attack a player other than you if able.)
Whenever one or more creatures attack one of your opponents, those creatures gain menace until end of turn.

Sludge Titan

Trample
Whenever Sludge Titan enters or attacks, mill five cards. You may put a creature card and/or a land card from among them into your hand.

Covetous Elegy

Each player chooses up to two creatures they control, then sacrifices the rest. Then you create a tapped Treasure token for each creature your opponents control.

Niv-Mizzet, Guildpact

Flying, hexproof from multicolored
Whenever Niv-Mizzet, Guildpact deals combat damage to a player, it deals X damage to any target, target player draws X cards, and you gain X life, where X is the number of different color pairs among permanents you control that are exactly two colors.

Incriminating Impetus

Enchant creature
When Incriminating Impetus enters, suspect enchanted creature. (It has menace and can't block.)
Enchanted creature gets +2/+2 and is goaded. (It attacks each combat if able and attacks a player other than you if able.)