Legate Lanius, Caesar's Ace

Decimate — When Legate Lanius enters, each opponent sacrifices a tenth of the creatures they control of their choice, rounded up.
Whenever an opponent sacrifices a creature, put a +1/+1 counter on Legate Lanius.

Overseer of Vault 76

First Contact — Whenever Overseer of Vault 76 or another creature you control with power 3 or less enters, put a quest counter on Overseer of Vault 76.
At the beginning of combat on your turn, you may remove three quest counters from among permanents you control. When you do, put a +1/+1 counter on each creature you control and they gain vigilance until end of turn.

Elder Arthur Maxson

Creature tokens you control have training. (Whenever a creature token you control attacks with another creature with greater power, put a +1/+1 counter on that token.)
Blind Betrayal — Sacrifice another creature: Elder Arthur Maxson gains indestructible until end of turn.

Boomer Scrapper

Whenever Boomer Scrapper enters or attacks, you lose 1 life and create a Junk token. (It's an artifact with "{T}, Sacrifice this artifact: Exile the top card of your library. You may play that card this turn. Activate only as a sorcery.")
Whenever a token you control leaves the battlefield, put a +1/+1 counter on Boomer Scrapper.

ED-E, Lonesome Eyebot

Flying
ED-E My Love — Whenever you attack, if the number of attacking creatures is greater than the number of quest counters on ED-E, Lonesome Eyebot, put a quest counter on it.
{2}, Sacrifice ED-E: Draw a card, then draw an additional card for each quest counter on ED-E.

Desdemona, Freedom's Edge

Vigilance
Whenever Desdemona, Freedom's Edge attacks, target creature card in your graveyard that's an artifact or that has mana value 3 or less gains escape until end of turn. The escape cost is equal to its mana cost plus exile two other cards from your graveyard. (You may cast it from your graveyard for its escape cost this turn.)

Pitiless Plunderer

Whenever another creature you control dies, create a Treasure token. (It's an artifact with "{T}, Sacrifice this artifact: Add one mana of any color.")

Butch DeLoria, Tunnel Snake

Menace (This creature can't be blocked except by two or more creatures.)
Tunnel Snakes Rule! — Whenever Butch DeLoria, Tunnel Snake attacks, it gets +1/+1 until end of turn for each other Rogue and/or Snake you control.
{1}{B}: Put a menace counter on another target creature. It becomes a Rogue in addition to its other types.

Craig Boone, Novac Guard

Reach, lifelink
One for My Baby — Whenever you attack with two or more creatures, put two quest counters on Craig Boone, Novac Guard. When you do, Craig Boone deals damage equal to the number of quest counters on it to up to one target creature unless that creature's controller has Craig Boone deal that much damage to them.

Mr. House, President and CEO

Whenever you roll a 4 or higher, create a 3/3 colorless Robot artifact creature token. If you rolled 6 or higher, instead create that token and a Treasure token.
{4}, {T}: Roll a six-sided die plus an additional six-sided die for each mana from Treasures spent to activate this ability.

Captain of the Watch

Vigilance (Attacking doesn't cause this creature to tap.)
Other Soldier creatures you control get +1/+1 and have vigilance.
When Captain of the Watch enters, create three 1/1 white Soldier creature tokens.

Colonel Autumn

Lifelink
Exploit (When this creature enters, you may sacrifice a creature.)
Other legendary creatures you control have exploit.
Whenever a creature you control exploits a creature, put a +1/+1 counter on each creature you control.

General's Enforcer

Legendary Humans you control have indestructible.
{2}{W}{B}: Exile target card from a graveyard. If it was a creature card, create a 1/1 white Human Soldier creature token.

MacCready, Lamplight Mayor

Whenever a creature you control with power 2 or less attacks, it gains skulk until end of turn. (It can't be blocked by creatures with greater power.)
Whenever a creature with power 4 or greater attacks you, its controller loses 2 life and you gain 2 life.

Aradesh, the Founder

Enlist (As this creature attacks, you may tap a nonattacking creature you control without summoning sickness. When you do, add its power to this creature's until end of turn.)
Whenever a creature you control attacks, if it enlisted a creature this combat, the creature that attacked gains double strike until end of turn. If that creature's power is 4 or greater, draw a card.

Morbid Opportunist

Whenever one or more other creatures die, draw a card. This ability triggers only once each turn.

Kellogg, Dangerous Mind

First strike, haste
Whenever Kellogg, Dangerous Mind attacks, create a Treasure token.
Sacrifice five Treasures: Gain control of target creature for as long as you control Kellogg. Activate only as a sorcery.

Mysterious Stranger

Flash
When Mysterious Stranger enters, for each graveyard with an instant or sorcery card in it, exile target instant or sorcery card from that graveyard. If two or more cards are exiled this way, choose one of them at random and copy it. You may cast the copy without paying its mana cost.

Caesar, Legion's Emperor

Whenever you attack, you may sacrifice another creature. When you do, choose two —
• Create two 1/1 red and white Soldier creature tokens with haste that are tapped and attacking.
• You draw a card and you lose 1 life.
• Caesar, Legion's Emperor deals damage equal to the number of creature tokens you control to target opponent.

Gary Clone

Squad {2} (As an additional cost to cast this spell, you may pay {2} any number of times. When this creature enters, create that many tokens that are copies of it.)
Whenever Gary Clone attacks, each creature you control named Gary Clone gets +1/+0 until end of turn.

Impassioned Orator

Whenever another creature you control enters, you gain 1 life.

Paladin Elizabeth Taggerdy

Battalion — Whenever Paladin Elizabeth Taggerdy and at least two other creatures attack, draw a card, then you may put a creature card with mana value X or less from your hand onto the battlefield tapped and attacking, where X is Paladin Elizabeth Taggerdy's power.

Keeper of the Accord

At the beginning of each opponent's end step, if that player controls more creatures than you, create a 1/1 white Soldier creature token.
At the beginning of each opponent's end step, if that player controls more lands than you, you may search your library for a basic Plains card, put it onto the battlefield tapped, then shuffle.