Mnemonic Wall

Defender
When Mnemonic Wall enters the battlefield, you may return target instant or sorcery card from your graveyard to your hand.

Overgrown Battlement

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

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.)

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.

Arcades, the Strategist

Flying, vigilance
Whenever a creature with defender enters the battlefield under your control, 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.

Wall of Glare

Defender (This creature can't attack.)
Wall of Glare can block any number of creatures.

Towering Titan

Towering Titan enters the battlefield with X +1/+1 counters on it, where X is the total toughness of other creatures you control.
Sacrifice a creature with defender: All creatures gain trample until end of turn.

Wall of Denial

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

Wingmantle Chaplain

Defender
When Wingmantle Chaplain enters the battlefield, create a 1/1 white Bird creature token with flying for each creature with defender you control.
Whenever another creature with defender enters the battlefield under your control, create a 1/1 white Bird creature token with flying.

Crashing Drawbridge

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

Wall

Wall of Runes

Defender (This creature can't attack.)
When Wall of Runes enters the battlefield, scry 1. (Look at the top card of your library. You may put that card on the bottom of your library.)

Wall of Stolen Identity

You may have Wall of Stolen Identity enter the battlefield as a copy of any creature on the battlefield, except it's a Wall in addition to its other types and has defender. When you do, tap the copied creature and it doesn't untap during its controller's untap step for as long as you control Wall of Stolen Identity.

Shield-Wall Sentinel

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