Coastal Breach

Undaunted (This spell costs {1} less to cast for each opponent.)
Return all nonland permanents to their owners' hands.

Belbe, Corrupted Observer

At the beginning of each postcombat main phase, the active player adds {C}{C} for each of your opponents who lost life this turn. (Damage causes loss of life.)

Tyranid Invasion

Create a number of 3/3 green Tyranid Warrior creature tokens with trample equal to the number of opponents you have.

Silverwing Squadron

Flying, vigilance
Silverwing Squadron's power and toughness are each equal to the number of creatures you control.
Whenever this creature attacks, create a number of 2/2 white Knight creature tokens with vigilance equal to the number of opponents you have.

Communal Brewing

When this enchantment enters, any number of target opponents each draw a card. Put an ingredient counter on this enchantment, then put an ingredient counter on it for each card drawn this way.
Whenever you cast a creature spell, that creature enters with X additional +1/+1 counters on it, where X is the number of ingredient counters on this enchantment.

Curtains' Call

Undaunted (This spell costs {1} less to cast for each opponent.)
Destroy two target creatures.

Durnan of the Yawning Portal

Whenever Durnan attacks, look at the top four cards of your library. You may exile a creature card from among them. Put the rest on the bottom of your library in any order. For as long as that card remains exiled, you may cast it. That spell has undaunted. (It costs {1} less to cast for each opponent.)
Choose a Background (You can have a Background as a second commander.)

Primeval Protector

This spell costs {1} less to cast for each creature your opponents control.
When this creature enters, put a +1/+1 counter on each other creature you control.

Alexios, Deimos of Kosmos

Trample
Alexios attacks each combat if able, can't be sacrificed, and can't attack its owner.
At the beginning of each player's upkeep, that player gains control of Alexios, untaps it, and puts a +1/+1 counter on it. It gains haste until end of turn.

Managorger Hydra

Trample
Whenever a player casts a spell, put a +1/+1 counter on this creature.

Priest of the Blessed Graf

At the beginning of your end step, create X 1/1 white Spirit creature tokens with flying, where X is the number of opponents who control more lands than you.

Beledros Witherbloom

Flying
At the beginning of each upkeep, create a 1/1 black and green Pest creature token with "When this token dies, you gain 1 life."
Pay 10 life: Untap all lands you control. Activate only once each turn.

Ezuri's Predation

For each creature your opponents control, create a 4/4 green Phyrexian Beast creature token. Each of those tokens fights a different one of those creatures.

Sublime Exhalation

Undaunted (This spell costs {1} less to cast for each opponent.)
Destroy all creatures.

Tinybones Joins Up

When Tinybones Joins Up enters, any number of target players each discard a card.
Whenever a legendary creature you control enters, any number of target players each mill a card and lose 1 life.

Company Commander

Command Section — When this creature enters, create a number of 1/1 white Soldier creature tokens equal to the number of opponents you have.
Bring it Down! — Whenever this creature attacks, creatures you control gain deathtouch until end of turn.

Nezahal, Primal Tide

This spell can't be countered.
You have no maximum hand size.
Whenever an opponent casts a noncreature spell, draw a card.
Discard three cards: Exile Nezahal. Return it to the battlefield tapped under its owner's control at the beginning of the next end step.

Tymna the Weaver

Lifelink
At the beginning of each of your postcombat main phases, you may pay X life, where X is the number of opponents that were dealt combat damage this turn. If you do, draw X cards.
Partner (You can have two commanders if both have partner.)