We Ride at Dawn

Legendary creature spells you cast have convoke. (Your creatures can help cast those spells. Each creature you tap while casting a legendary creature spell pays for {1} or one mana of that creature's color.)
Whenever your commander attacks, create a 1/1 red Mercenary creature token with "{T}: Target creature you control gets +1/+0 until end of turn. Activate only as a sorcery."

Falthis, Shadowcat Familiar

Commanders you control have menace and deathtouch.
Partner (You can have two commanders if both have partner.)

Swords to Plowshares

Exile target creature. Its controller gains life equal to its power.

Hero's Heirloom

Equipped creature gets +2/+1.
As long as equipped creature is legendary, it has trample and haste.
Equip {2}

Duelist's Heritage

Whenever one or more creatures attack, you may have target attacking creature gain double strike until end of turn.

Aegis of the Gods

You have hexproof. (You can't be the target of spells or abilities your opponents control.)

Evolving Wilds

{T}, Sacrifice this land: Search your library for a basic land card, put it onto the battlefield tapped, then shuffle.

Brilliant Wings

Flash
Enchant creature you control
Enchanted creature has flying and hexproof.
Whenever a creature you control enters, you may pay {1}. If you do, attach this Aura to that creature.

Isamaru, Hound of Konda

Yoshimaru, Ever Faithful

Whenever another legendary permanent you control enters, put a +1/+1 counter on Yoshimaru.
Partner (You can have two commanders if both have partner.)

Path to Exile

Exile target creature. Its controller may search their library for a basic land card, put that card onto the battlefield tapped, then shuffle.

Day of Destiny

Legendary creatures you control get +2/+2.

Amazing Alliance

Creatures you control get +1/+1.
Whenever you attack with one or more legendary creatures, you gain that much life.

Case of the Stashed Skeleton

When this Case enters, create a 2/1 black Skeleton creature token and suspect it. (It has menace and can't block.)
To solve — You control no suspected Skeletons. (If unsolved, solve at the beginning of your end step.)
Solved — {1}{B}, Sacrifice this Case: Search your library for a card, put it into your hand, then shuffle. Activate only as a sorcery.

Orzhov Locket

{T}: Add {W} or {B}.
{W/B}{W/B}{W/B}{W/B}, {T}, Sacrifice this artifact: Draw two cards.

Brave the Sands

Creatures you control have vigilance.
Each creature you control can block an additional creature each combat.

Scoured Barrens

This land enters tapped.
When this land enters, you gain 1 life.
{T}: Add {W} or {B}.

Forsaken Sanctuary

This land enters tapped.
{T}: Add {W} or {B}.

Agent of the Shadow Thieves

Commander creatures you own have "Whenever this creature attacks a player, if no opponent has more life than that player, put a +1/+1 counter on this creature. It gains deathtouch and indestructible until end of turn."

Keleth, Sunmane Familiar

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

Sandstone Bridge

This land enters tapped.
When this land enters, target creature gets +1/+1 and gains vigilance until end of turn.
{T}: Add {W}.

Bleeding Effect

At the beginning of combat on your turn, creatures you control gain flying until end of turn if a creature card in your graveyard has flying. The same is true for first strike, double strike, deathtouch, hexproof, indestructible, lifelink, menace, reach, trample, and vigilance.

Always Watching

Nontoken creatures you control get +1/+1 and have vigilance.

Bad Moon

Sejiri Steppe

This land enters tapped.
When this land enters, target creature you control gains protection from the color of your choice until end of turn.
{T}: Add {W}.