Join forces — Starting with you, each player may pay any amount of mana. Each player searches their library for up to X basic land cards, where X is the total amount of mana paid this way, puts them onto the battlefield tapped, then shuffles their library.

: Add one mana of any color in your commander's color identity.

: Add one mana of any color in your commander's color identity.
Sacrifice Commander's Sphere: Draw a card.

Equipped creature gets +1/+1 for each color among permanents you control.
As long as Conqueror's Flail is attached to a creature, your opponents can't cast spells during your turn.
Equip

Consuming Aberration's power and toughness are each equal to the number of cards in your opponents' graveyards.
Whenever you cast a spell, each opponent reveals cards from the top of their library until they reveal a land card, then puts those cards into their graveyard.

If one or more +1/+1 counters would be put on a creature you control, twice that many +1/+1 counters are put on it instead.

Crackling Doom deals 2 damage to each opponent. Each opponent sacrifices a creature with the greatest power among creatures that player controls.

Equipped creature gets +1/+0 for each artifact you control.
: Attach Cranial Plating to target creature you control.
Equip

Choose target player and another target player. The first player controls the second player during the second player's next turn, and the second player controls the first player during the first player's next turn.

Crumbling Necropolis enters the battlefield tapped.
: Add , , or .

Converge — Crystalline Crawler enters the battlefield with a +1/+1 counter on it for each color of mana spent to cast it.
Remove a +1/+1 counter from Crystalline Crawler: Add one mana of any color.
: Put a +1/+1 counter on Crystalline Crawler.

Search your library for up to two basic land cards, reveal those cards, and put one onto the battlefield tapped and the other into your hand. Then shuffle your library.

Enchant player
Whenever enchanted player casts a spell, put a spite counter on Curse of Vengeance.
When enchanted player loses the game, you gain X life and draw X cards, where X is the number of spite counters on Curse of Vengeance.

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

Custodi Soulbinders enters the battlefield with X +1/+1 counters on it, where X is the number of other creatures on the battlefield.
, Remove a +1/+1 counter from Custodi Soulbinders: Create a 1/1 white Spirit creature token with flying.

[+2]: Discard up to two cards, then draw that many cards.
[−2]: Sacrifice an artifact. If you do, return target artifact card from your graveyard to the battlefield.
[−10]: You get an emblem with "Whenever an artifact is put into your graveyard from the battlefield, return that card to the battlefield at the beginning of the next end step."
Daretti, Scrap Savant can be your commander.

Indestructible
: Add .

Indestructible
: Add one mana of any color.

, : Add .

Sacrifice Dauntless Escort: Creatures you control gain indestructible until end of turn.