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.

Overgrown Battlement

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

Tetsuko Umezawa, Fugitive

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

Stalwart Shield-Bearers

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

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.

The Pride of Hull Clade

This spell costs {X} less to cast, where X is the total toughness of creatures you control.
Defender
{2}{U}{U}: Until end of turn, target creature you control gets +1/+0, gains "Whenever this creature deals combat damage to a player, draw cards equal to its toughness," and can attack as though it didn't have defender.

Sunscape Familiar

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

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.)

Wall of Blossoms

Defender
When Wall of Blossoms enters, draw a card.

Wall of Omens

Defender
When Wall of Omens enters, draw a card.

Sol Ring

Arcane Signet

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

Swords to Plowshares

Exile target creature. Its controller gains life equal to its power.

Fecund Greenshell

Reach
As long as you control ten or more lands, creatures you control get +2/+2.
Whenever Fecund Greenshell or another creature you control with toughness greater than its power enters, look at the top card of your library. If it's a land card, you may put it onto the battlefield tapped. Otherwise, put it into your hand.

Sokrates, Athenian Teacher

Defender
Sokrates, Athenian Teacher has hexproof as long as it's untapped.
Sokratic Dialogue — {T}: Until end of turn, target creature gains "If this creature would deal combat damage to a player, prevent that damage. This creature's controller and that player each draw half that many cards, rounded down."

Shield Sphere

Defender
Whenever Shield Sphere blocks, put a -0/-1 counter on it.

Bedrock Tortoise

During your turn, creatures you control have hexproof.
Each creature you control with toughness greater than its power assigns combat damage equal to its toughness rather than its power.

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.

Generous Gift

Destroy target permanent. Its controller creates a 3/3 green Elephant creature token.

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.

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.

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

The Battle of Bywater

Destroy all creatures with power 3 or greater. Then create a Food token for each creature you control. (It's an artifact with "{2}, {T}, Sacrifice this artifact: You gain 3 life.")