Black creatures get +1/+1.

Each creature gets +1/+1 for each other creature on the battlefield that shares at least one creature type with it. (For example, if two Goblin Warriors and a Goblin Shaman are on the battlefield, each gets +2/+2.)

Commander creatures you own have "Whenever this creature becomes tapped, it and other creatures you control that share a creature type with it each get +2/+0 and gain undying until end of turn." (When a creature with undying dies, if it had no +1/+1 counters on it, return it to the battlefield under its owner's control with a +1/+1 counter on it.)

Toxic 1 (Players dealt combat damage by this creature also get a poison counter.) Other Rats you control have toxic 1. When Karumonix enters the battlefield, look at the top five cards of your library. You may reveal any number of Rat cards from among them and put the revealed cards into your hand. Put the rest on the bottom of your library in a random order.

{1}{B}, {T}, Sacrifice another creature: Draw X cards, where X is that creature's power. Choose a Background (You can have a Background as a second commander.)

({T}: Add {B}.)

{T}: Add one mana of any color in your commander's color identity.

Black creature spells you cast cost {1} less to cast. Whenever you cast a creature spell, each opponent loses 1 life and you gain 1 life.

As Herald's Horn enters the battlefield, choose a creature type. Creature spells you cast of the chosen type cost {1} less to cast. At the beginning of your upkeep, look at the top card of your library. If it's a creature card of the chosen type, you may reveal it and put it into your hand.

As Heraldic Banner enters the battlefield, choose a color. Creatures you control of the chosen color get +1/+0. {T}: Add one mana of the chosen color.

Black spells you cast cost {1} less to cast.

{T}: Add {C}. {1}, {T}, Sacrifice Mind Stone: Draw a card.

{T}: Add {C}{C}.

Pack Rat's power and toughness are each equal to the number of Rats you control. {2}{B}, Discard a card: Create a token that's a copy of Pack Rat.

Return target creature card and all other cards with the same name as that card from your graveyard to your hand.

At the beginning of your upkeep, if you have four or more creature cards in your graveyard, you may return target creature card from your graveyard to your hand.

Each player chooses a creature type. Each player returns all creature cards of a type chosen this way from their graveyard to the battlefield.

{1}{B}, Pay 2 life: Return target creature card from your graveyard to your hand.

Choose one — • Return target creature card from your graveyard to your hand. • Return two target creature cards that share a creature type from your graveyard to your hand.

Choose one — • Return target creature card from your graveyard to your hand. • Return two target creature cards that share a creature type from your graveyard to your hand.

As an additional cost to cast this spell, discard a card or pay 3 life. Destroy target creature or planeswalker.

Choose a creature type. Creatures that aren't of the chosen type get -3/-3 until end of turn.

Target creature gets -1/-1 until end of turn for each Swamp you control.

Destroy target creature or enchantment an opponent controls. You lose life equal to that permanent's mana value.

As Cover of Darkness enters the battlefield, choose a creature type. Creatures of the chosen type have fear. (They can't be blocked except by artifact creatures and/or black creatures.)

All Rats have fear. {T}, Sacrifice a Rat: Create X 1/1 black Rat creature tokens, where X is the number of Rats you control.

Whenever another nontoken creature dies, you may create a 1/1 black Rat creature token. Rats you control have deathtouch.

Whenever Ayara, First of Locthwain or another black creature enters the battlefield under your control, each opponent loses 1 life and you gain 1 life. {T}, Sacrifice another black creature: Draw a card.