The Walls of Ba Sing Se

Defender
Other permanents you control have indestructible.

Mystic Barrier

When this enchantment enters and at the beginning of your upkeep, choose left or right.
Each player may attack only the nearest opponent in the last chosen direction and planeswalkers controlled by that opponent.

Day of the Dragons

When this enchantment enters, exile all creatures you control. Then create that many 5/5 red Dragon creature tokens with flying.
When this enchantment leaves the battlefield, sacrifice all Dragons you control. Then return the exiled cards to the battlefield under your control.

Teyo, the Shieldmage

You have hexproof. (You can't be the target of spells or abilities your opponents control.)
−2: Create a 0/3 white Wall creature token with defender.

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.

Aetherflame Wall

Defender
This creature can block creatures with shadow as though they didn't have shadow.
{R}: This creature gets +1/+0 until end of turn.

Pramikon, Sky Rampart

Flying, defender
As Pramikon enters, choose left or right.
Each player may attack only the nearest opponent in the chosen direction and planeswalkers controlled by that opponent.

Shield Sphere

Defender
Whenever this creature blocks, put a -0/-1 counter on it.

Angelic Wall

Defender (This creature can't attack.)
Flying

Battle Rampart

Defender
{T}: Target creature gains haste until end of turn.

Aether Membrane

Defender; reach (This creature can block creatures with flying.)
Whenever this creature blocks a creature, return that creature to its owner's hand at end of combat.

Sol Ring

Court of Ire

When this enchantment enters, you become the monarch.
At the beginning of your upkeep, this enchantment deals 2 damage to any target. If you're the monarch, it deals 7 damage instead.

Fortified Area

Wall creatures you control get +1/+0 and have banding. (Any creatures with banding, and up to one without, can attack in a band. Bands are blocked as a group. If any creatures with banding you control are blocking or being blocked by a creature, you divide that creature's combat damage, not its controller, among any of the creatures it's being blocked by or is blocking.)

Wall of Denial

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

Meekstone

Creatures with power 3 or greater don't untap during their controllers' untap steps.

Gleaming Barrier

Defender
When this creature dies, create a Treasure token. (It's an artifact with "{T}, Sacrifice this token: Add one mana of any color.")