Ashcoat Bear

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

Pale Bears

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

Striped Bears

When Striped Bears enters the battlefield, draw a card.

Balduvian Bears

Druid's Familiar

Soulbond (You may pair this creature with another unpaired creature when either enters the battlefield. 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.

Bear Cub

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.

Ulvenwald Bear

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

Duskana, the Rage Mother

When Duskana, the Rage Mother enters the battlefield, 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.