Keyword: Partner

Whenever Armix, Filigree Thrasher attacks, you may discard a card. When you do, target creature defending player controls gets -X/-X until end of turn, where X is the number of artifacts you control plus the number of artifact cards in your graveyard.
Partner (You can have two commanders if both have partner.)

+2: Create two 0/1 black Thrull creature tokens.
+1: You may sacrifice another creature or planeswalker. If you do, draw two cards, then draw another card if the sacrificed permanent was a commander.
−10: Gain control of all commanders. Put all commanders from the command zone onto the battlefield under your control.
Tevesh Szat, Doom of Fools can be your commander.
Partner

, Sacrifice three other artifacts and/or creatures: Look at the top three cards of your library. Put two of them into your hand and the other into your graveyard.
Partner (You can have two commanders if both have partner.)

Flying
Other creatures you control get +1/+1.
At the beginning of your upkeep, you may return target creature card from your graveyard to your hand.
Partner (You can have two commanders if both have partner.)

Whenever Miara, Thorn of the Glade or another Elf you control dies, you may pay and 1 life. If you do, draw a card.
Partner (You can have two commanders if both have partner.)

When Alharu, Solemn Ritualist enters the battlefield, put a +1/+1 counter on each of up to two other target creatures.
Whenever a nontoken creature you control with a +1/+1 counter on it dies, create a 1/1 white Spirit creature token with flying.
Partner (You can have two commanders if both have partner.)

When Alharu, Solemn Ritualist enters the battlefield, put a +1/+1 counter on each of up to two other target creatures.
Whenever a nontoken creature you control with a +1/+1 counter on it dies, create a 1/1 white Spirit creature token with flying.
Partner (You can have two commanders if both have partner.)

Flying
Whenever Siani, Eye of the Storm attacks, scry X, where X is the number of attacking creatures with flying.
Partner (You can have two commanders if both have partner.)

As long as it’s your turn, commanders you control have indestructible. (Effects that say “destroy” don’t destroy them. A creature with indestructible can’t be destroyed by damage.)
Partner (You can have two commanders if both have partner.)

If The Prismatic Piper is your commander, choose a color before the game begins. The Prismatic Piper is the chosen color.
Partner (You can have two commanders if both have partner.)

Whenever a commander you control attacks, put a +1/+1 counter on it.
Partner (You can have two commanders if both have partner.)

Whenever a land enters the battlefield under your control, create a colorless Equipment artifact token named Rock with “Equipped creature has ‘, , Sacrifice Rock: This creature deals 2 damage to any target'” and equip .
Partner (You can have two commanders if both have partner.)

You may have Sakashima of a Thousand Faces enter the battlefield as a copy of another creature you control, except it has Sakashima of a Thousand Faces’s other abilities.
The “legend rule” doesn’t apply to permanents you control.
Partner (You can have two commanders if both have partner.)

As long as it’s your turn, commanders you control have indestructible. (Effects that say “destroy” don’t destroy them. A creature with indestructible can’t be destroyed by damage.)
Partner (You can have two commanders if both have partner.)

Whenever you cast your first spell each turn, choose an opponent at random. Vial Smasher the Fierce deals damage equal to that spell’s converted mana cost to that player or a planeswalker that player controls.
Partner (You can have two commanders if both have partner.)

: Choose another target creature. Its controller may exile it with an aegis counter on it.
, : Return all exiled cards with aegis counters on them to the battlefield under their owners’ control.
Partner (You can have two commanders if both have partner.)

First strike
: Add an amount of equal to the greatest power among creatures you control that entered the battlefield this turn.
Partner (You can have two commanders if both have partner.)

Flying, haste
Whenever an opponent casts their second spell each turn, draw a card.
Partner (You can have two commanders if both have partner.)

: Add . When you spend this mana to cast a spell with converted mana cost 6 or greater, draw a card.
Partner (You can have two commanders if both have partner.)

Reach
Whenever another permanent enters the battlefield under your control, if it wasn’t put onto the battlefield with this ability, you may put a permanent card with equal or lesser converted mana cost from your hand onto the battlefield.
Partner (You can have two commanders if both have partner.)

Flying
Whenever another creature dies, put two +1/+1 counters on Sengir, the Dark Baron.
Whenever another player loses the game, you gain life equal to that player’s life total as the turn began.
Partner (You can have two commanders if both have partner.)

First strike, menace, trample
Partner (You can have two commanders if both have partner.)

Partner with Gorm the Great (When this creature enters the battlefield, target player may put Gorm into their hand from their library, then shuffle.)
Deathtouch
Whenever Virtus the Veiled deals combat damage to a player, that player loses half their life, rounded up.

Partner with Virtus the Veiled (When this creature enters the battlefield, target player may put Virtus into their hand from their library, then shuffle.)
Vigilance
Gorm the Great must be blocked if able, and Gorm must be blocked by two or more creatures if able.

Partner with Shabraz, the Skyshark (When this creature enters the battlefield, target player may put Shabraz into their hand from their library, then shuffle.)
Whenever you discard a card, put a +1/+1 counter on Brallin, Skyshark Rider and it deals 1 damage to each opponent.
: Target Shark gains trample until end of turn.