Boros Mastiff

Battalion — Whenever Boros Mastiff and at least two other creatures attack, Boros Mastiff gains lifelink until end of turn. (Damage dealt by a creature with lifelink also causes its controller to gain that much life.)

Isamaru, Hound of Konda

Karlov Watchdog

Vigilance
Permanents your opponents control can't be turned face up during your turn.
Whenever you attack with three or more creatures, creatures you control get +1/+1 until end of turn.

Dreadhound

When Dreadhound enters, mill three cards. (Put the top three cards of your library into your graveyard.)
Whenever a creature dies or a creature card is put into a graveyard from a library, each opponent loses 1 life.

Alpine Watchdog

Vigilance (Attacking doesn't cause this creature to tap.)

Ghost Hounds

Vigilance
Whenever Ghost Hounds blocks or becomes blocked by a white creature, Ghost Hounds gains first strike until end of turn.

Blink Dog

Double strike
Teleport — {3}{W}: Blink Dog phases out. (Treat it and anything attached to it as though they don't exist until your next turn.)

Pack Leader

Other Dogs you control get +1/+1.
Whenever Pack Leader attacks, prevent all combat damage that would be dealt this turn to Dogs you control.

Resolute Watchdog

Defender
{1}, Sacrifice Resolute Watchdog: Target creature you control gains indestructible until end of turn. (Damage and effects that say "destroy" don't destroy it.)

Encampment Keeper

First strike
{7}{W}, {T}, Sacrifice Encampment Keeper: Creatures you control get +2/+2 until end of turn.

Hollowborn Barghest

At the beginning of your upkeep, if you have no cards in hand, each opponent loses 2 life.
At the beginning of each opponent's upkeep, if that player has no cards in hand, they lose 2 life.

Akroan Mastiff

Phelia, Exuberant Shepherd

Flash
Whenever Phelia, Exuberant Shepherd attacks, exile up to one other target nonland permanent. At the beginning of the next end step, return that card to the battlefield under its owner's control. If it entered under your control, put a +1/+1 counter on Phelia.

Kunoros, Hound of Athreos

Vigilance, menace, lifelink
Creature cards in graveyards can't enter the battlefield.
Players can't cast spells from graveyards.

Mischievous Pup

Flash (You may cast this spell any time you could cast an instant.)
When this creature enters, return up to one other target permanent you control to its owner's hand.

Guard Dogs

{2}{W}, {T}: Choose a permanent you control. Prevent all combat damage target creature would deal this turn if it shares a color with that permanent.

Yoshimaru, Ever Faithful

Whenever another legendary permanent you control enters, put a +1/+1 counter on Yoshimaru, Ever Faithful.
Partner (You can have two commanders if both have partner.)

Cathar's Companion

Whenever you cast a noncreature spell, Cathar's Companion gains indestructible until end of turn. (Damage and effects that say "destroy" don't destroy it.)