Vine Kami

Menace (This creature can't be blocked except by two or more creatures.)
Soulshift 6 (When this creature dies, you may return target Spirit card with mana value 6 or less from your graveyard to your hand.)

Invoke the Ancients

Create two 4/5 green Spirit creature tokens. For each of them, put your choice of a vigilance counter, a reach counter, or a trample counter on it.

Baleful Eidolon

Bestow {4}{B} (If you cast this card for its bestow cost, it's an Aura spell with enchant creature. It becomes a creature again if it's not attached to a creature.)
Deathtouch (Any amount of damage this deals to a creature is enough to destroy it.)
Enchanted creature gets +1/+1 and has deathtouch.

Thief of Hope

Whenever you cast a Spirit or Arcane spell, target opponent loses 1 life and you gain 1 life.
Soulshift 2 (When this creature dies, you may return target Spirit card with mana value 2 or less from your graveyard to your hand.)

Cultivate

Search your library for up to two basic land cards, reveal those cards, put one onto the battlefield tapped and the other into your hand, then shuffle.

Venerable Kumo

Reach (This creature can block creatures with flying.)
Soulshift 4 (When this creature dies, you may return target Spirit card with mana value 4 or less from your graveyard to your hand.)

Pus Kami

{B}, Sacrifice Pus Kami: Destroy target nonblack creature.
Soulshift 6 (When this creature dies, you may return target Spirit card with mana value 6 or less from your graveyard to your hand.)

Kami of Empty Graves

Soulshift 3 (When this creature dies, you may return target Spirit card with mana value 3 or less from your graveyard to your hand.)

Forked-Branch Garami

Soulshift 4, soulshift 4 (When this creature dies, you may return up to two target Spirit cards with mana value 4 or less from your graveyard to your hand.)

Kami of the Tended Garden

At the beginning of your upkeep, sacrifice Kami of the Tended Garden unless you pay {G}.
Soulshift 3 (When this creature dies, you may return target Spirit card with mana value 3 or less from your graveyard to your hand.)

Nightsoil Kami

Soulshift 5 (When this creature dies, you may return target Spirit card with mana value 5 or less from your graveyard to your hand.)

Sengir, the Dark Baron

Flying
Whenever another creature dies, put two +1/+1 counters on Sengir, the Dark Baron.
Whenever another player loses the game, you gain life equal to that player's life total as the turn began.
Partner (You can have two commanders if both have partner.)

Rootrunner

{G}{G}, Sacrifice Rootrunner: Put target land on top of its owner's library.
Soulshift 3 (When this creature dies, you may return target Spirit card with mana value 3 or less from your graveyard to your hand.)

Arcane Signet

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

Deathknell Kami

Flying
{2}: Deathknell Kami gets +1/+1 until end of turn. Sacrifice it at the beginning of the next end step.
Soulshift 1 (When this creature dies, you may return target Spirit card with mana value 1 or less from your graveyard to your hand.)

Kin-Tree Invocation

Create an X/X black and green Spirit Warrior creature token, where X is the greatest toughness among creatures you control.

Thousand-legged Kami

Soulshift 7 (When this creature dies, you may return target Spirit card with mana value 7 or less from your graveyard to your hand.)

Command Tower

Consume Spirit

Spend only black mana on X.
Consume Spirit deals X damage to any target and you gain X life.

He Who Hungers

Flying
{1}, Sacrifice a Spirit: Target opponent reveals their hand. You choose a card from it. That player discards that card. Activate only as a sorcery.
Soulshift 4 (When this creature dies, you may return target Spirit card with mana value 4 or less from your graveyard to your hand.)

Scuttling Death

Sacrifice Scuttling Death: Target creature gets -1/-1 until end of turn.
Soulshift 4 (When this creature dies, you may return target Spirit card with mana value 4 or less from your graveyard to your hand.)

Burr Grafter

Sacrifice Burr Grafter: Target creature gets +2/+2 until end of turn.
Soulshift 3 (When this creature dies, you may return target Spirit card with mana value 3 or less from your graveyard to your hand.)

Kodama of the Center Tree

Kodama of the Center Tree's power and toughness are each equal to the number of Spirits you control.
Kodama of the Center Tree has soulshift X, where X is the number of Spirits you control. (When this creature dies, you may return target Spirit card with mana value X or less from your graveyard to your hand.)

Kami of Lunacy

Flying
Soulshift 5 (When this creature dies, you may return target Spirit card with mana value 5 or less from your graveyard to your hand.)

Body of Jukai

Trample
Soulshift 8 (When this creature dies, you may return target Spirit card with mana value 8 or less from your graveyard to your hand.)

Elder Pine of Jukai

Whenever you cast a Spirit or Arcane spell, reveal the top three cards of your library. Put all land cards revealed this way into your hand and the rest on the bottom of your library in any order.
Soulshift 2 (When this creature dies, you may return target Spirit card with mana value 2 or less from your graveyard to your hand.)

Kodama of the East Tree

Reach
Whenever another permanent enters the battlefield under your control, if it wasn't put onto the battlefield with this ability, you may put a permanent card with equal or lesser mana value from your hand onto the battlefield.
Partner (You can have two commanders if both have partner.)

Crawling Filth

Fear (This creature can't be blocked except by artifact creatures and/or black creatures.)
Soulshift 5 (When this creature dies, you may return target Spirit card with mana value 5 or less from your graveyard to your hand.)

Bloodghast

Bloodghast can't block.
Bloodghast has haste as long as an opponent has 10 or less life.
Landfall — Whenever a land enters the battlefield under your control, you may return Bloodghast from your graveyard to the battlefield.

Harbinger of Spring

Protection from non-Spirit creatures
Soulshift 4 (When this creature dies, you may return target Spirit card with mana value 4 or less from your graveyard to your hand.)

Ayumi, the Last Visitor

Legendary landwalk (This creature can't be blocked as long as defending player controls a legendary land.)

Gibbering Kami

Flying
Soulshift 3 (When this creature dies, you may return target Spirit card with mana value 3 or less from your graveyard to your hand.)

Unchecked Growth

Target creature gets +4/+4 until end of turn. If it's a Spirit, it gains trample until end of turn.