Druid's Familiar

Soulbond (You may pair this creature with another unpaired creature when either enters. They remain paired for as long as you control both of them.)
As long as Druid's Familiar is paired with another creature, each of those creatures gets +2/+2.

Ruxa, Patient Professor

Whenever Ruxa, Patient Professor enters or attacks, return target creature card with no abilities from your graveyard to your hand.
Creatures you control with no abilities get +1/+1.
For each creature you control with no abilities, you may have that creature assign its combat damage as though it weren't blocked.

Ulvenwald Bear

Morbid — When Ulvenwald Bear enters, if a creature died this turn, put two +1/+1 counters on target creature.

Ursine Champion

{5}{G}: Ursine Champion gets +3/+3 and becomes a Bear Berserker until end of turn. Activate only once each turn.

Wilson, Refined Grizzly

This spell can't be countered.
Vigilance, reach, trample
Ward {2} (Whenever this creature becomes the target of a spell or ability an opponent controls, counter it unless that player pays {2}.)
Choose a Background (You can have a Background as a second commander.)

Ayula, Queen Among Bears

Whenever another Bear you control enters, choose one —
• Put two +1/+1 counters on target Bear.
• Target Bear you control fights target creature you don't control.

Mother Bear

{3}{G}{G}, Exile Mother Bear from your graveyard: Create two 2/2 green Bear creature tokens. Activate only as a sorcery.

Rampaging Yao Guai

Vigilance, trample
Rampaging Yao Guai enters with X +1/+1 counters on it.
When Rampaging Yao Guai enters, destroy any number of target artifacts and/or enchantments with total mana value X or less.

Pale Bears

Islandwalk (This creature can't be blocked as long as defending player controls an Island.)

Caller of the Claw

Flash
When Caller of the Claw enters, create a 2/2 green Bear creature token for each nontoken creature put into your graveyard from the battlefield this turn.

Bearscape

{1}{G}, Exile two cards from your graveyard: Create a 2/2 green Bear creature token.

Ayula's Influence

Discard a land card: Create a 2/2 green Bear creature token.

Welcome Home

Create three 2/2 green Bear creature tokens. (Then exile this card. You may cast the creature later from exile.)

Flaxen Intruder

Whenever Flaxen Intruder deals combat damage to a player, you may sacrifice it. When you do, destroy target artifact or enchantment.

Flaxen Intruder // Welcome Home

Woodland Changeling

Changeling (This card is every creature type.)

Grizzly Bears

Herald's Horn

As Herald's Horn enters, choose a creature type.
Creature spells you cast of the chosen type cost {1} less to cast.
At the beginning of your upkeep, look at the top card of your library. If it's a creature card of the chosen type, you may reveal it and put it into your hand.

Arcane Signet

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

Duskana, the Rage Mother

When Duskana, the Rage Mother enters, draw a card for each creature you control with base power and toughness 2/2.
Whenever a creature you control with base power and toughness 2/2 attacks, it gets +3/+3 until end of turn.

Adaptive Automaton

As this creature enters, choose a creature type.
This creature is the chosen type in addition to its other types.
Other creatures you control of the chosen type get +1/+1.

Kudo, King Among Bears

Other creatures have base power and toughness 2/2 and are Bears in addition to their other types.

Bloodline Pretender

Changeling (This card is every creature type.)
As Bloodline Pretender enters, choose a creature type.
Whenever another creature you control of the chosen type enters, put a +1/+1 counter on Bloodline Pretender.

Swiftfoot Boots

Equipped creature has hexproof and haste. (It can't be the target of spells or abilities your opponents control. It can attack and {T} no matter when it came under your control.)
Equip {1} ({1}: Attach to target creature you control. Equip only as a sorcery.)

Grizzly Fate

Create two 2/2 green Bear creature tokens.
Threshold — Create four 2/2 green Bear creature tokens instead if seven or more cards are in your graveyard.
Flashback {5}{G}{G} (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Surrak and Goreclaw

Trample
Other creatures you control have trample.
Whenever another nontoken creature you control enters, put a +1/+1 counter on it. It gains haste until end of turn.

Lightning Greaves

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

Archetype of Courage

Creatures you control have first strike.
Creatures your opponents control lose first strike and can't have or gain first strike.

Balduvian Bears

Avian Changeling

Changeling (This card is every creature type.)
Flying

Tuya Bearclaw

Whenever Tuya Bearclaw attacks, it gets +X/+X until end of turn, where X is the greatest power among other creatures you control.

Goblin Anarchomancer

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

Bear Cub

Worldly Tutor

Search your library for a creature card, reveal it, then shuffle and put the card on top.

Ashcoat Bear

Flash (You may cast this spell any time you could cast an instant.)

Irregular Cohort

Changeling (This card is every creature type.)
When Irregular Cohort enters, create a 2/2 colorless Shapeshifter creature token with changeling.

Sol Ring

Forest Bear

Runeclaw Bear

Urza's Incubator

As Urza's Incubator enters, choose a creature type.
Creature spells of the chosen type cost {2} less to cast.

Manglehorn

When Manglehorn enters, you may destroy target artifact.
Artifacts your opponents control enter tapped.

Beast Whisperer

Whenever you cast a creature spell, draw a card.

Quirion Beastcaller

Whenever you cast a creature spell, put a +1/+1 counter on Quirion Beastcaller.
When Quirion Beastcaller dies, distribute X +1/+1 counters among any number of target creatures you control, where X is the number of +1/+1 counters on Quirion Beastcaller.