Kodama of the South Tree

Whenever you cast a Spirit or Arcane spell, each other creature you control gets +1/+1 and gains trample until end of turn.

Supreme Phantom

Flying
Other Spirits you control get +1/+1.

Blood Age General

{T}: Attacking Spirits get +1/+0 until end of turn.

Hofri Ghostforge

Spirits you control get +1/+1 and have trample and haste.
Whenever another nontoken creature you control dies, exile it. If you do, create a token that's a copy of that creature, except it's a Spirit in addition to its other types and it has "When this creature leaves the battlefield, return the exiled card to its owner's graveyard."

Angel of Flight Alabaster

Flying
At the beginning of your upkeep, return target Spirit card from your graveyard to your hand.

Rukarumel, Biologist

As Rukarumel, Biologist enters the battlefield, choose a creature type.
Slivers you control and nontoken creatures you control are the chosen type in addition to their other creature types. The same is true for creature spells you control and creature cards you own that aren't on the battlefield.
{3}, {T}: Create a 1/1 colorless Sliver creature token.

Breath of the Sleepless

You may cast Spirit spells as though they had flash.
Whenever you cast a creature spell during an opponent's turn, tap up to one target creature.

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.)

Bounteous Kirin

Flying
Whenever you cast a Spirit or Arcane spell, you may gain life equal to that spell's mana value.

Briarknit Kami

Whenever you cast a Spirit or Arcane spell, put a +1/+1 counter on target creature.

Lifespinner

{T}, Sacrifice three Spirits: Search your library for a legendary Spirit permanent card, put it onto the battlefield, then shuffle.