Wall of Diffusion

Defender (This creature can't attack.)
Wall of Diffusion can block creatures with shadow as though Wall of Diffusion had shadow.

Aetherflame Wall

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

Crenellated Wall

Defender (This creature can't attack.)
{T}: Target creature gets +0/+4 until end of turn.

Living Wall

Defender (This creature can't attack.)
{1}: Regenerate Living Wall.

Wall of Bone

Defender (This creature can't attack.)
{B}: Regenerate Wall of Bone. (The next time this creature would be destroyed this turn, instead tap it, remove it from combat, and heal all damage on it.)

Amaranthine Wall

Defender
{2}: Amaranthine Wall gains indestructible until end of turn. (Damage and effects that say "destroy" don't destroy it.)

Steel Wall

Pitchstone Wall

Defender (This creature can't attack.)
Whenever you discard a card, you may sacrifice Pitchstone Wall. If you do, return the discarded card from your graveyard to your hand.

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.

Shifting Wall

Defender (This creature can't attack.)
Shifting Wall enters with X +1/+1 counters on it.

Moaning Wall

Defender
Cycling {2} ({2}, Discard this card: Draw a card.)

Wall of Blood

Defender (This creature can't attack.)
Pay 1 life: Wall of Blood gets +1/+1 until end of turn.

Walking Wall

Defender
{3}: Walking Wall gets +3/-1 until end of turn and can attack this turn as though it didn't have defender. Activate only once each turn.

Wall of Fire

Defender (This creature can't attack.)
{R}: Wall of Fire gets +1/+0 until end of turn.

Flowstone Wall

Defender (This creature can't attack.)
{R}: Flowstone Wall gets +1/-1 until end of turn.

Wall of Earth

Excavated Wall

Defender
{1}, {T}: Mill a card. (Put the top card of your library into your graveyard.)