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.)

Lifecreed Duo

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

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.)

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.

Glidedive Duo

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

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.

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.

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.)

Marching Duodrone

Whenever Marching Duodrone attacks, each player creates a Treasure token. (It's an artifact with "{T}, Sacrifice this artifact: Add one mana of any color.")

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.)

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.

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.

Brave-Kin Duo

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

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.)

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.)