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.

Stoic Ephemera

Defender (This creature can't attack.)
Flying
When Stoic Ephemera blocks, sacrifice it at end of combat.

Island

Wall of Frost

Defender
Whenever Wall of Frost blocks a creature, that creature doesn't untap during its controller's next untap step.

Soulbound Guardians

Plains

Warmonger's Chariot

Equipped creature gets +2/+2.
As long as equipped creature has defender, it can attack as though it didn't have defender.
Equip {3} ({3}: Attach to target creature you control. Equip only as a sorcery.)

Amaranthine Wall

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

Ludevic's Abomination

Ludevic's Test Subject

Defender
{1}{U}: Put a hatchling counter on Ludevic's Test Subject. Then if there are five or more hatchling counters on it, remove all of them and transform it.

Ludevic's Test Subject // Ludevic's Abomination

Doorkeeper

Defender
{2}{U}, {T}: Target player mills X cards, where X is the number of creatures you control with defender.

Guardian of the Ages

Defender (This creature can't attack.)
When a creature attacks you or a planeswalker you control, if Guardian of the Ages has defender, it loses defender and gains trample.

Manor Gargoyle

Defender
Manor Gargoyle has indestructible as long as it has defender.
{1}: Until end of turn, Manor Gargoyle loses defender and gains flying.

Midnight Clock

{T}: Add {U}.
{2}{U}: Put an hour counter on Midnight Clock.
At the beginning of each upkeep, put an hour counter on Midnight Clock.
When the twelfth hour counter is put on Midnight Clock, shuffle your hand and graveyard into your library, then draw seven cards. Exile Midnight Clock.

Wall of Lost Thoughts

Defender (This creature can't attack.)
When Wall of Lost Thoughts enters, target player mills four cards. (They put the top four cards of their library into their graveyard.)

Gomazoa

Defender, flying
{T}: Put Gomazoa and each creature it's blocking on top of their owners' libraries, then those players shuffle.

Folio of Fancies

Players have no maximum hand size.
{X}{X}, {T}: Each player draws X cards.
{2}{U}, {T}: Each opponent mills cards equal to the number of cards in their hand.

Phantasmal Abomination

Defender
When Phantasmal Abomination becomes the target of a spell or ability, sacrifice it.

Cathedral Membrane

({W/P} can be paid with either {W} or 2 life.)
Defender
When Cathedral Membrane dies during combat, it deals 6 damage to each creature it blocked this combat.