Thallid Shell-Dweller

Defender
At the beginning of your upkeep, put a spore counter on this creature.
Remove three spore counters from this creature: Create a 1/1 green Saproling creature token.

Vitaspore Thallid

At the beginning of your upkeep, put a spore counter on this creature.
Remove three spore counters from this creature: Create a 1/1 green Saproling creature token.
Sacrifice a Saproling: Target creature gains haste until end of turn.

Rootborn Defenses

Populate. Creatures you control gain indestructible until end of turn. (To populate, create a token that's a copy of a creature token you control.)

Sundering Growth

Destroy target artifact or enchantment, then populate. (Create a token that's a copy of a creature token you control.)

Overgrown Armasaur

Enrage — Whenever this creature is dealt damage, create a 1/1 green Saproling creature token.

Scatter the Seeds

Convoke (Your creatures can help cast this spell. Each creature you tap while casting this spell pays for {1} or one mana of that creature's color.)
Create three 1/1 green Saproling creature tokens.

Thallid

At the beginning of your upkeep, put a spore counter on this creature.
Remove three spore counters from this creature: Create a 1/1 green Saproling creature token.

Pallid Mycoderm

At the beginning of your upkeep, put a spore counter on this creature.
Remove three spore counters from this creature: Create a 1/1 green Saproling creature token.
Sacrifice a Saproling: Each creature you control that's a Fungus or a Saproling gets +1/+1 until end of turn.

Thallid Germinator

At the beginning of your upkeep, put a spore counter on this creature.
Remove three spore counters from this creature: Create a 1/1 green Saproling creature token.
Sacrifice a Saproling: Target creature gets +1/+1 until end of turn.

Undercellar Myconid

Whenever this creature enters or dies, create a 1/1 green Saproling creature token.
{T}: Add one mana of any color.