Reki, the History of Kamigawa

Whenever you cast a legendary spell, draw a card.

Heartless Hidetsugu

{T}: Heartless Hidetsugu deals damage to each player equal to half that player's life total, rounded down.

Toggo, Goblin Weaponsmith

Landfall — Whenever a land you control enters, create a colorless Equipment artifact token named Rock with "Equipped creature has '{1}, {T}, Sacrifice Rock: This creature deals 2 damage to any target'" and equip {1}.
Partner (You can have two commanders if both have partner.)

Syr Alin, the Lion's Claw

First strike (This creature deals combat damage before creatures without first strike.)
Whenever Syr Alin attacks, other creatures you control get +1/+1 until end of turn.

Masumaro, First to Live

Masumaro's power and toughness are each equal to twice the number of cards in your hand.

Stangg, Echo Warrior

Whenever Stangg attacks, create Stangg Twin, a legendary 3/4 red and green Human Warrior creature token. It enters tapped and attacking. For each Aura and Equipment attached to Stangg, create a token that's a copy of it attached to Stangg Twin. Sacrifice all tokens created this way at the beginning of the next end step.

Munda, Ambush Leader

Haste
Rally — Whenever Munda or another Ally you control enters, you may look at the top four cards of your library. If you do, reveal any number of Ally cards from among them, then put those cards on top of your library in any order and the rest on the bottom in any order.

Cait, Cage Brawler

During your turn, Cait has indestructible.
Whenever Cait attacks, you and defending player each draw a card, then discard a card. Put two +1/+1 counters on Cait if you discarded the card with the greatest mana value among those cards or tied for greatest.

Dosan the Falling Leaf

Players can cast spells only during their own turns.

Erkenbrand, Lord of Westfold

Whenever Erkenbrand or another Human you control enters, creatures you control get +1/+0 until end of turn.

Stangg

When Stangg enters, create Stangg Twin, a legendary 3/4 red and green Human Warrior creature token. Exile that token when Stangg leaves the battlefield. Sacrifice Stangg when that token leaves the battlefield.

Homura's Essence

Creatures you control get +2/+2 and have flying and "{R}: This creature gets +1/+0 until end of turn."

Homura, Human Ascendant

Homura can't block.
When Homura dies, return it to the battlefield flipped.

Homura, Human Ascendant // Homura's Essence

Strax, Sontaran Nurse

Vigilance, trample
Grenades! — {2}, {T}, Sacrifice an artifact: Choose a player at random. When you do, Strax fights another target creature that player controls.
Glory of Battle — Whenever Strax deals damage to a creature, put a +1/+1 counter on Strax.

Surtr, Fiery Jötun

Trample (This creature can deal excess combat damage to the player it's attacking.)
Whenever you cast a historic spell, Surtr deals 3 damage to any target. (Artifacts, legendaries, and Sagas are historic.)

Iwamori of the Open Fist

Trample
When Iwamori enters, each opponent may put a legendary creature card from their hand onto the battlefield.

Gorm the Great

Partner with Virtus the Veiled (When this creature enters, target player may put Virtus into their hand from their library, then shuffle.)
Vigilance
Gorm must be blocked if able, and Gorm must be blocked by two or more creatures if able.

Osgir, the Reconstructor

Vigilance
{1}, Sacrifice an artifact: Target creature you control gets +2/+0 until end of turn.
{X}, {T}, Exile an artifact card with mana value X from your graveyard: Create two tokens that are copies of the exiled card. Activate only as a sorcery.

Minsc, Beloved Ranger

When Minsc enters, create Boo, a legendary 1/1 red Hamster creature token with trample and haste.
{X}: Until end of turn, target creature you control has base power and toughness X/X and becomes a Giant in addition to its other types. Activate only as a sorcery.

Rasaad yn Bashir

Each creature you control assigns combat damage equal to its toughness rather than its power.
Whenever Rasaad yn Bashir attacks, if you have the initiative, double the toughness of each creature you control until end of turn.
Choose a Background (You can have a Background as a second commander.)