Hipparion

Hipparion can't block creatures with power 3 or greater unless you pay {1}.

Diamond Mare

As Diamond Mare enters, choose a color.
Whenever you cast a spell of the chosen color, you gain 1 life.

Chrome Steed

Metalcraft — Chrome Steed gets +2/+2 as long as you control three or more artifacts.

Clockwork Steed

Clockwork Steed enters with four +1/+0 counters on it.
Clockwork Steed can't be blocked by artifact creatures.
At end of combat, if Clockwork Steed attacked or blocked this combat, remove a +1/+0 counter from it.
{X}, {T}: Put up to X +1/+0 counters on Clockwork Steed. This ability can't cause the total number of +1/+0 counters on Clockwork Steed to be greater than four. Activate only during your upkeep.

Bronze Horse

Trample
As long as you control another creature, prevent all damage that would be dealt to Bronze Horse by spells that target it.

Akroan Horse

Defender
When Akroan Horse enters, an opponent gains control of it.
At the beginning of your upkeep, each opponent creates a 1/1 white Soldier creature token.

Dwarven Pony

{1}{R}, {T}: Target Dwarf creature gains mountainwalk until end of turn. (It can't be blocked as long as defending player controls a Mountain.)

Shadowfax, Lord of Horses

Horses you control have haste. (They can attack and {T} as soon as they come under your control.)
Whenever Shadowfax, Lord of Horses attacks, you may put a creature card with lesser power from your hand onto the battlefield tapped and attacking.

Bill the Pony

When Bill the Pony enters, create two Food tokens. (They're artifacts with "{2}, {T}, Sacrifice this artifact: You gain 3 life.")
Sacrifice a Food: Until end of turn, target creature you control assigns combat damage equal to its toughness rather than its power.

Crested Sunmare

Other Horses you control have indestructible.
At the beginning of each end step, if you gained life this turn, create a 5/5 white Horse creature token.

Armored Warhorse

Lightning Mare

This spell can't be countered.
Lightning Mare can't be blocked by blue creatures.
{1}{R}: Lightning Mare gets +1/+0 until end of turn.

Calamity, Galloping Inferno

Haste
Whenever Calamity, Galloping Inferno attacks while saddled, choose a nonlegendary creature that saddled it this turn and create a tapped and attacking token that's a copy of it. Sacrifice that token at the beginning of the next end step. Repeat this process once.
Saddle 1