Crashing Drawbridge

Defender
{T}: Creatures you control gain haste until end of turn.

Plains

Herald of Hoofbeats

Horsemanship (This creature can't be blocked except by creatures with horsemanship.)
Other Knights you control have horsemanship.

Lionheart Maverick

Vigilance
{4}{W}: This creature gets +1/+2 until end of turn.

Gideon, Ally of Zendikar

+1: Until end of turn, Gideon becomes a 5/5 Human Soldier Ally creature with indestructible that's still a planeswalker. Prevent all damage that would be dealt to him this turn.
0: Create a 2/2 white Knight Ally creature token.
−4: You get an emblem with "Creatures you control get +1/+1."

Paladin Class

(Gain the next level as a sorcery to add its ability.)
Spells your opponents cast during your turn cost {1} more to cast.
{2}{W}: Level 2
Creatures you control get +1/+1.
{4}{W}: Level 3
Whenever you attack, until end of turn, target attacking creature gets +1/+1 for each other attacking creature and gains double strike.

Knight Exemplar

First strike (This creature deals combat damage before creatures without first strike.)
Other Knight creatures you control get +1/+1 and have indestructible. (Damage and effects that say "destroy" don't destroy them.)

Prairie Stream

({T}: Add {W} or {U}.)
This land enters tapped unless you control two or more basic lands.

Azorius Chancery

This land enters tapped.
When this land enters, return a land you control to its owner's hand.
{T}: Add {W}{U}.

Guardian of Faith

Flash
Vigilance
When this creature enters, any number of other target creatures you control phase out. (Treat them and anything attached to them as though they don't exist until their controller's next turn.)

Symmetry Matrix

Whenever a creature you control with power equal to its toughness enters, you may pay {1}. If you do, draw a card.

Westfold Rider

Sacrifice this creature: Destroy target artifact or enchantment. Activate only as a sorcery.

Enchant creature
Enchanted creature gets +2/+2, has first strike, and is a Knight in addition to its other types. (It deals combat damage before creatures without first strike.)

Vodalian Wave-Knight

Whenever you draw a card, put a +1/+1 counter on each other Merfolk and/or Knight you control.

Knight of the White Orchid

First strike
When this creature enters, if an opponent controls more lands than you, you may search your library for a Plains card, put it onto the battlefield, then shuffle.

Mirran Crusader

Double strike, protection from black and from green

Ajani's Welcome

Whenever a creature you control enters, you gain 1 life.

Idyllic Beachfront

({T}: Add {W} or {U}.)
This land enters tapped.

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}

Skycloud Expanse

Vanquisher's Banner

As this artifact enters, choose a creature type.
Creatures you control of the chosen type get +1/+1.
Whenever you cast a creature spell of the chosen type, draw a card.

Temple of Enlightenment

This land enters tapped.
When this land enters, scry 1. (Look at the top card of your library. You may put that card on the bottom.)
{T}: Add {W} or {U}.

Student of Warfare

Level up {W} ({W}: Put a level counter on this. Level up only as a sorcery.)
LEVEL 2-6
3/3
First strike
LEVEL 7+
4/4
Double strike

Vertex Paladin

Flying
Vertex Paladin's power and toughness are each equal to the number of creatures you control.

Invasion of Xerex

(As a Siege enters, choose an opponent to protect it. You and others can attack it. When it's defeated, exile it, then cast it transformed.)
When this Siege enters, return up to one target creature to its owner's hand.

Invasion of Xerex // Vertex Paladin

Tranquil Cove

This land enters tapped.
When this land enters, you gain 1 life.
{T}: Add {W} or {U}.

Worthy Knight

Whenever you cast a Knight spell, create a 1/1 white Human creature token.

Teferi Akosa of Zhalfir

+1: Draw two cards. Then discard two cards unless you discard a creature card.
−2: You get an emblem with "Knights you control get +1/+0 and have ward {1}."
−3: Tap any number of untapped creatures you control. When you do, shuffle target nonland permanent an opponent controls with mana value X or less into its owner's library, where X is the number of creatures tapped this way.

Invasion of New Phyrexia

(As a Siege enters, choose an opponent to protect it. You and others can attack it. When it's defeated, exile it, then cast it transformed.)
When this Siege enters, create X 2/2 white and blue Knight creature tokens with vigilance.

Invasion of New Phyrexia // Teferi Akosa of Zhalfir

Thistledown Liege

Flash
Other white creatures you control get +1/+1.
Other blue creatures you control get +1/+1.

Marshal of Zhalfir

Other Knights you control get +1/+1.
{W}{U}, {T}: Tap another target creature.

Hour of Reckoning

Convoke (Your creatures can help cast this spell. Each creature you tap while casting this spell pays for {1} or one mana of that creature's color.)
Destroy all nontoken creatures.

New Benalia

This land enters tapped.
When this land enters, scry 1. (Look at the top card of your library. You may put that card on the bottom.)
{T}: Add {W}.

History of Benalia

(As this Saga enters and after your draw step, add a lore counter. Sacrifice after III.)
I, II — Create a 2/2 white Knight creature token with vigilance.
III — Knights you control get +2/+1 until end of turn.