Ulvenwald Bear

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

Runeclaw Bear

Bear Cub

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.

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.

Argoth, Sanctum of Nature

Argoth, Sanctum of Nature enters tapped unless you control a legendary green creature.
{T}: Add {G}.
{2}{G}{G}, {T}: Create a 2/2 green Bear creature token, then mill three cards. Activate only as a sorcery.
(Melds with Titania, Voice of Gaea.)

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.

Aggressive Instinct

Target creature you control deals damage equal to its power to target creature you don't control.

Ayula's Influence

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

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.)

Owlbear

Trample
Keen Senses — When Owlbear enters, draw a card.

Alpha Status

Enchant creature
Enchanted creature gets +2/+2 for each other creature on the battlefield that shares a creature type with it.

Halsin, Emerald Archdruid

{1}: Until end of turn, target token you control becomes a green Bear creature with base power and toughness 4/4 in addition to its other colors and types.
Choose a Background (You can have a Background as a second commander.)

Owlbear Cub

Mama's Coming — Whenever Owlbear Cub attacks a player who controls eight or more lands, look at the top eight cards of your library. You may put a creature card from among them onto the battlefield tapped and attacking that player. Put the rest on the bottom of your library in a random order.

Ashcoat Bear

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

Werebear

{T}: Add {G}.
Threshold — Werebear gets +3/+3 as long as seven or more cards are in your graveyard.

Casal, Pathbreaker Owlbear

Vigilance, trample
When this creature transforms into Casal, Pathbreaker Owlbear, other legendary creatures you control get +2/+2 and gain trample until end of turn.
At the beginning of your upkeep, transform Doric.

Casal, Lurkwood Pathfinder

Vigilance
When Casal enters, search your library for a Forest card, put it onto the battlefield tapped, then shuffle.
Whenever Doric attacks, you may pay {1}{G}. If you do, transform her.

Casal, Lurkwood Pathfinder // Casal, Pathbreaker Owlbear

Master Chef

Commander creatures you own have "This creature enters with an additional +1/+1 counter on it" and "Other creatures you control enter with an additional +1/+1 counter on them."

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.

Acorn Harvest

Create two 1/1 green Squirrel creature tokens.
Flashback—{1}{G}, Pay 3 life. (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Aim High

Untap target creature. It gets +2/+2 and gains reach until end of turn. (It can block creatures with flying.)

Circle of the Moon Druid

Bear Form — During your turn, Circle of the Moon Druid is a Bear with base power and toughness 4/2. (It loses all other creature types.)

Copper Host Crusher

Trample
Hexproof (This creature can't be the target of spells or abilities your opponents control.)

Alpha Authority

Enchant creature
Enchanted creature has hexproof and can't be blocked by more than one creature.

Professor of Zoomancy

When Professor of Zoomancy enters, create a 1/1 black and green Pest creature token with "When this creature dies, you gain 1 life."

Aerial Predation

Destroy target creature with flying. You gain 2 life.

Abundant Harvest

Choose land or nonland. Reveal cards from the top of your library until you reveal a card of the chosen kind. Put that card into your hand and the rest on the bottom of your library in a random order.

Mother Bear

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

Abundant Growth

Enchant land
When Abundant Growth enters, draw a card.
Enchanted land has "{T}: Add one mana of any color."

Striped Bears

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.

Goreclaw, Terror of Qal Sisma

Creature spells you cast with power 4 or greater cost {2} less to cast.
Whenever Goreclaw, Terror of Qal Sisma attacks, each creature you control with power 4 or greater gets +1/+1 and gains trample until end of turn.