Stalwart Shield-Bearers

Defender
Other creatures you control with defender get +0/+2.

Command Tower

{T}: Add one mana of any color in your commander's color identity.

Tower Defense

Creatures you control get +0/+5 and gain reach until end of turn.

Overgrown Battlement

Defender
{T}: Add {G} for each creature you control with defender.

Hover Barrier

Tetsuko Umezawa, Fugitive

Creatures you control with power or toughness 1 or less can't be blocked.

Exotic Orchard

{T}: Add one mana of any color that a land an opponent controls could produce.

High Alert

Each creature you control assigns combat damage equal to its toughness rather than its power.
Creatures you control can attack as though they didn't have defender.
{2}{W}{U}: Untap target creature.

Wall of Omens

Defender
When Wall of Omens enters, draw a card.

Island

Axebane Guardian

Defender
{T}: Add X mana in any combination of colors, where X is the number of creatures you control with defender.

Wall of Denial

Defender, flying
Shroud (This creature can't be the target of spells or abilities.)

Forest

Wall of Blossoms

Defender
When Wall of Blossoms enters, draw a card.

Dawn

Aftermath (Cast this spell only from your graveyard. Then exile it.)
Return all creature cards with power 2 or less from your graveyard to your hand.

Dusk

Destroy all creatures with power 3 or greater.

Dusk // Dawn

Shield-Wall Sentinel

Defender
When Shield-Wall Sentinel enters, you may search your library for a creature card with defender, reveal it, put it into your hand, then shuffle.

Jeskai Barricade

Flash (You may cast this spell any time you could cast an instant.)
Defender
When Jeskai Barricade enters, you may return another target creature you control to its owner's hand.

Crashing Drawbridge

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

Assault Formation

Each creature you control assigns combat damage equal to its toughness rather than its power.
{G}: Target creature with defender can attack this turn as though it didn't have defender.
{2}{G}: Creatures you control get +0/+1 until end of turn.

Plains

Perimeter Captain

Defender
Whenever a creature you control with defender blocks, you may gain 2 life.

Sunscape Familiar

Defender (This creature can't attack.)
Green spells and blue spells you cast cost {1} less to cast.

Arcades, the Strategist

Flying, vigilance
Whenever a creature you control with defender enters, draw a card.
Each creature you control with defender assigns combat damage equal to its toughness rather than its power and can attack as though it didn't have defender.

Slaughter the Strong

Each player chooses any number of creatures they control with total power 4 or less, then sacrifices all other creatures they control.

Rammas Echor, Ancient Shield

Whenever you cast your second spell each turn, draw a card, then create a 0/3 white Wall creature token with defender.
At the beginning of combat on your turn, creatures you control with defender gain exalted until end of turn. (Whenever a creature you control attacks alone, it gets +1/+1 until end of turn for each instance of exalted among permanents you control.)