Xenosquirrels

This creature enters with two +1/+1 counters on it.
After you roll a die, you may remove a +1/+1 counter from this creature. If you do, increase or decrease the result by 1.

Chatterfang, Squirrel General

Forestwalk (This creature can't be blocked as long as defending player controls a Forest.)
If one or more tokens would be created under your control, those tokens plus that many 1/1 green Squirrel creature tokens are created instead.
{B}, Sacrifice X Squirrels: Target creature gets +X/-X until end of turn.

Ivy Lane Denizen

Whenever another green creature you control enters, put a +1/+1 counter on target creature.

Command Tower

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

Squirrel Sanctuary

When this enchantment enters, create a 1/1 green Squirrel creature token.
Whenever a nontoken creature you control dies, you may pay {1}. If you do, return this enchantment to its owner's hand.

Squirrel Nest

Enchant land
Enchanted land has "{T}: Create a 1/1 green Squirrel creature token."

Squirrel Wrangler

{1}{G}, Sacrifice a land: Create two 1/1 green Squirrel creature tokens.
{1}{G}, Sacrifice a land: Squirrel creatures get +1/+1 until end of turn.

Squirrel Sovereign

Cloakwood Hermit

Commander creatures you own have "At the beginning of your end step, if a creature card was put into your graveyard from anywhere this turn, create two tapped 1/1 green Squirrel creature tokens."

Squirrel Mob

This creature gets +1/+1 for each other Squirrel on the battlefield.

Nature's Lore

Search your library for a Forest card, put that card onto the battlefield, then shuffle.

Chatter of the Squirrel

Create a 1/1 green Squirrel creature token.
Flashback {1}{G} (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Ravenous Squirrel

Whenever you sacrifice an artifact or creature, put a +1/+1 counter on this creature.
{1}{B}{G}, Sacrifice an artifact or creature: You gain 1 life and draw a card.

Shadowheart, Dark Justiciar

{1}{B}, {T}, Sacrifice another creature: Draw X cards, where X is that creature's power.
Choose a Background (You can have a Background as a second commander.)