Starnheim Courser

Flying
Artifact and enchantment spells you cast cost {1} less to cast.

Kambal, Consul of Allocation

Whenever an opponent casts a noncreature spell, that player loses 2 life and you gain 2 life.

Anafenza, the Foremost

Whenever Anafenza, the Foremost attacks, put a +1/+1 counter on another target tapped creature you control.
If a nontoken creature an opponent owns would die or a creature card not on the battlefield would be put into an opponent's graveyard, exile that card instead.

Flawless Maneuver

If you control a commander, you may cast this spell without paying its mana cost.
Creatures you control gain indestructible until end of turn.

Setessan Champion

Constellation — Whenever an enchantment enters the battlefield under your control, put a +1/+1 counter on Setessan Champion and draw a card.

Arcane Signet

{T}: Add one mana of any color in your commander's color identity.

Calix, Guided by Fate

Constellation — Whenever Calix, Guided by Fate or another enchantment enters the battlefield under your control, put a +1/+1 counter on target creature.
Whenever Calix or an enchanted creature you control deals combat damage to a player, you may create a token that's a copy of a nonlegendary enchantment you control. Do this only once each turn.

Doran, the Siege Tower

Each creature assigns combat damage equal to its toughness rather than its power.

Behind the Scenes

Creatures you control have skulk. (They can't be blocked by creatures with greater power.)
{4}{W}: Creatures you control get +1/+1 until end of turn.

Kosei, Penitent Warlord

As long as Kosei, Penitent Warlord is enchanted, equipped, and has a counter on it, Kosei has "Whenever Kosei, Penitent Warlord deals combat damage to an opponent, you draw that many cards and Kosei deals that much damage to each other opponent."

Mirri, Weatherlight Duelist

First strike
Whenever Mirri, Weatherlight Duelist attacks, each opponent can't block with more than one creature this combat.
As long as Mirri, Weatherlight Duelist is tapped, no more than one creature can attack you each combat.

Mox Amber

{T}: Add one mana of any color among legendary creatures and planeswalkers you control.