Marshal of Zhalfir

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

Swordsworn Cavalier

Swordsworn Cavalier has first strike as long as another Knight entered the battlefield under your control this turn.

Zhalfirin Lancer

Whenever another Knight you control enters, Zhalfirin Lancer gets +1/+1 and gains vigilance until end of turn.

Elspeth's Smite

Elspeth's Smite deals 3 damage to target attacking or blocking creature. If that creature would die this turn, exile it instead.

Island

Meeting of Minds

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.)
Draw two cards.

Protocol Knight

When Protocol Knight enters, tap target creature an opponent controls. Put a stun counter on that creature if you control another Knight. (If a permanent with a stun counter would become untapped, remove one from it instead.)

Sigiled Sentinel

Backup 1 (When this creature enters, put a +1/+1 counter on target creature. If that's another creature, it gains the following ability until end of turn.)
Vigilance

Belenon War Anthem

Invasion of Belenon

(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 Invasion of Belenon enters, create a 2/2 white and blue Knight creature token with vigilance.

Invasion of Belenon // Belenon War Anthem

Scrollshift

Exile up to one target artifact, creature, or enchantment you control, then return it to the battlefield under its owner's control.
Draw a card.

Venerable Knight

When Venerable Knight dies, put a +1/+1 counter on target Knight you control.

Plains

Artistic Refusal

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.)
Choose one or both —
• Counter target spell.
• Draw two cards, then discard a card.

Xerex Strobe-Knight

Flying, vigilance
{T}: Create a 2/2 white and blue Knight creature token with vigilance. Activate only if you've cast two or more spells this turn.

Angelic Intervention

Target creature or planeswalker you control gains protection from colorless or from the color of your choice until end of turn. If it's a creature, put a +1/+1 counter on it. (It can't be blocked, targeted, dealt damage, enchanted, or equipped by anything with that quality.)

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 Invasion of New Phyrexia enters, create X 2/2 white and blue Knight creature tokens with vigilance.

Invasion of New Phyrexia // Teferi Akosa of Zhalfir

Knight of the New Coalition

Vigilance
When Knight of the New Coalition enters, create a 2/2 white and blue Knight creature token with vigilance.