Minsc & Boo, Timeless Heroes

When Minsc & Boo enters and at the beginning of your upkeep, you may create Boo, a legendary 1/1 red Hamster creature token with trample and haste.
+1: Put three +1/+1 counters on up to one target creature with trample or haste.
−2: Sacrifice a creature. When you do, Minsc & Boo deals X damage to any target, where X is that creature's power. If the sacrificed creature was a Hamster, draw X cards.
Minsc & Boo, Timeless Heroes can be your commander.

Sword of the Squeak

Equipped creature gets +1/+1 for each creature you control with base power or toughness 1.
Whenever a Hamster, Mouse, Rat, or Squirrel you control enters, you may attach this Equipment to that creature.
Equip {2}

Kami of Whispered Hopes

If one or more +1/+1 counters would be put on a permanent you control, that many plus one +1/+1 counters are put on that permanent instead.
{T}: Add X mana of any one color, where X is this creature's power.

The Ozolith

Whenever a creature you control leaves the battlefield, if it had counters on it, put those counters on The Ozolith.
At the beginning of combat on your turn, if The Ozolith has counters on it, you may move all counters from The Ozolith onto target creature.

Chaos Warp

The owner of target permanent shuffles it into their library, then reveals the top card of their library. If it's a permanent card, they put it onto the battlefield.

Forgotten Ancient

Whenever a player casts a spell, you may put a +1/+1 counter on this creature.
At the beginning of your upkeep, you may move any number of +1/+1 counters from this creature onto other creatures.

Birds of Paradise

Primal Vigor

If one or more tokens would be created, twice that many of those tokens are created instead.
If one or more +1/+1 counters would be put on a creature, twice that many +1/+1 counters are put on that creature instead.

Band Together

Up to two target creatures you control each deal damage equal to their power to another target creature.

Rhythm of the Wild

Creature spells you control can't be countered.
Nontoken creatures you control have riot. (They enter with your choice of a +1/+1 counter or haste.)

Goblin Anarchomancer

Each spell you cast that's red or green costs {1} less to cast.

Lightning Greaves

Equipped creature has haste and shroud. (It can't be the target of spells or abilities.)
Equip {0}

Ancient Tomb

{T}: Add {C}{C}. This land deals 2 damage to you.

Halana and Alena, Partners

First strike (This creature deals combat damage before creatures without first strike.)
Reach (This creature can block creatures with flying.)
At the beginning of combat on your turn, put X +1/+1 counters on another target creature you control, where X is Halana and Alena's power. That creature gains haste until end of turn.

Sol Ring

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.

Fling

As an additional cost to cast this spell, sacrifice a creature.
Fling deals damage equal to the sacrificed creature's power to any target.

Branching Evolution

If one or more +1/+1 counters would be put on a creature you control, twice that many +1/+1 counters are put on that creature instead.

Hardened Scales

If one or more +1/+1 counters would be put on a creature you control, that many plus one +1/+1 counters are put on it instead.

Beast Within

Destroy target permanent. Its controller creates a 3/3 green Beast creature token.

Rolling Hamsphere

This Vehicle gets +1/+1 for each Hamster you control.
Whenever this Vehicle attacks, create three 1/1 red Hamster creature tokens, then it deals X damage to any target, where X is the number of Hamsters you control.
Crew 3

Nature's Lore

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

Unleash Fury

Double the power of target creature until end of turn.

Berserk

Cast this spell only before the combat damage step.
Target creature gains trample and gets +X/+0 until end of turn, where X is its power. At the beginning of the next end step, destroy that creature if it attacked this turn.

Rampant Growth

Search your library for a basic land card, put that card onto the battlefield tapped, then shuffle.

Llanowar Elves

Taurean Mauler

Changeling (This card is every creature type.)
Whenever an opponent casts a spell, you may put a +1/+1 counter on this creature.

Blasphemous Act

This spell costs {1} less to cast for each creature on the battlefield.
Blasphemous Act deals 13 damage to each creature.