Valiant Knight

Other Knights you control get +1/+1.
{3}{W}{W}: Knights you control gain double strike until end of turn.

Plains

Boros Guildgate

Boros Guildgate enters tapped.
{T}: Add {R} or {W}.

White Knight

First strike (This creature deals combat damage before creatures without first strike.)
Protection from black (This creature can't be blocked, targeted, dealt damage, or enchanted by anything black.)

Sigiled Sword of Valeron

Equipped creature gets +2/+0, has vigilance, and is a Knight in addition to its other types.
Whenever equipped creature attacks, create a 2/2 white Knight creature token with vigilance that's attacking.
Equip {3}

Boros Garrison

Boros Garrison enters tapped.
When Boros Garrison enters, return a land you control to its owner's hand.
{T}: Add {R}{W}.

Sylvia Brightspear

Partner with Khorvath Brightflame (When this creature enters, target player may put Khorvath into their hand from their library, then shuffle.)
Double strike
Dragons your team controls have double strike.

Clifftop Retreat

Clifftop Retreat enters tapped unless you control a Mountain or a Plains.
{T}: Add {R} or {W}.

Gisela, Blade of Goldnight

Flying, first strike
If a source would deal damage to an opponent or a permanent an opponent controls, that source deals double that damage to that player or permanent instead.
If a source would deal damage to you or a permanent you control, prevent half that damage, rounded up.

Lathliss, Dragon Queen

Flying
Whenever another nontoken Dragon you control enters, create a 5/5 red Dragon creature token with flying.
{1}{R}: Dragons you control get +1/+0 until end of turn.

Odric, Lunarch Marshal

At the beginning of each combat, creatures you control gain first strike until end of turn if a creature you control has first strike. The same is true for flying, deathtouch, double strike, haste, hexproof, indestructible, lifelink, menace, reach, skulk, trample, and vigilance.

Benalish Marshal

Khorvath Brightflame

Partner with Sylvia Brightspear (When this creature enters, target player may put Sylvia into their hand from their library, then shuffle.)
Flying, haste
Knights your team controls have flying and haste.

Archetype of Courage

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

Mountain

Archetype of Aggression

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