Emberstrike Duo

Whenever you cast a black spell, Emberstrike Duo gets +1/+1 until end of turn.
Whenever you cast a red spell, Emberstrike Duo gains first strike until end of turn.

Kenrith, the Returned King

{R}: All creatures gain trample and haste until end of turn.
{1}{G}: Put a +1/+1 counter on target creature.
{2}{W}: Target player gains 5 life.
{3}{U}: Target player draws a card.
{4}{B}: Put target creature card from a graveyard onto the battlefield under its owner's control.

Gravelgill Duo

Whenever you cast a blue spell, Gravelgill Duo gets +1/+1 until end of turn.
Whenever you cast a black spell, Gravelgill Duo gains fear until end of turn. (It can't be blocked except by artifact creatures and/or black creatures.)

Kindlespark Duo

{T}: Kindlespark Duo deals 1 damage to target opponent.
Whenever you cast a noncreature spell, untap Kindlespark Duo.

Roughshod Duo

Trample
Whenever you expend 4, target creature you control gets +1/+1 and gains trample until end of turn. (You expend 4 as you spend your fourth total mana to cast spells during a turn.)

Thistledown Duo

Whenever you cast a white spell, Thistledown Duo gets +1/+1 until end of turn.
Whenever you cast a blue spell, Thistledown Duo gains flying until end of turn.

Cecily, Haunted Mage

Your maximum hand size is eleven.
Whenever Cecily, Haunted Mage attacks, you draw a card and you lose 1 life. Then if you have eleven or more cards in your hand, you may cast an instant or sorcery spell from your hand without paying its mana cost.
Friends forever (You can have two commanders if both have friends forever.)

Glidedive Duo

Flying
When Glidedive Duo enters, each opponent loses 2 life and you gain 2 life.

Othelm, Sigardian Outcast

{2}, {T}: Choose target creature card in your graveyard that was put there from the battlefield this turn. Return it to the battlefield tapped.
Friends forever (You can have two commanders if both have friends forever.)

Safehold Duo

Whenever you cast a green spell, Safehold Duo gets +1/+1 until end of turn.
Whenever you cast a white spell, Safehold Duo gains vigilance until end of turn.

Treeguard Duo

When Treeguard Duo enters, until end of turn, target creature you control gains vigilance and gets +X/+X, where X is the number of creatures you control.

Skyskipper Duo

Flying
When Skyskipper Duo enters, exile up to one other target creature you control. Return it to the battlefield under its owner's control at the beginning of the next end step.

Lifecreed Duo

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

Tattermunge Duo

Whenever you cast a red spell, Tattermunge Duo gets +1/+1 until end of turn.
Whenever you cast a green spell, Tattermunge Duo gains forestwalk until end of turn. (It can't be blocked as long as defending player controls a Forest.)

Daggerfang Duo

Deathtouch
When Daggerfang Duo enters, you may mill two cards. (You may put the top two cards of your library into your graveyard.)

Bakersbane Duo

When Bakersbane Duo enters, create a Food token.
Whenever you expend 4, Bakersbane Duo gets +1/+1 until end of turn. (You expend 4 as you spend your fourth total mana to cast spells during a turn.)

Lightshell Duo

Prowess (Whenever you cast a noncreature spell, this creature gets +1/+1 until end of turn.)
When Lightshell Duo enters, surveil 2. (Look at the top two cards of your library, then put any number of them into your graveyard and the rest on top of your library in any order.)

The Prismatic Bridge

At the beginning of your upkeep, reveal cards from the top of your library until you reveal a creature or planeswalker card. Put that card onto the battlefield and the rest on the bottom of your library in a random order.

Esika, God of the Tree

Vigilance
{T}: Add one mana of any color.
Other legendary creatures you control have vigilance and "{T}: Add one mana of any color."

Esika, God of the Tree // The Prismatic Bridge

Brave-Kin Duo

{1}, {T}: Target creature gets +1/+1 until end of turn. Activate only as a sorcery.

Spellweaver Duo

Assist (Another player can pay up to {6} of this spell's cost.)
When Spellweaver Duo enters, you may return target tapped creature to its owner's hand.

Fiendish Duo

First strike
If a source would deal damage to an opponent, it deals double that damage to that player instead.