Locked in the Cemetery

Enchant creature
When Locked in the Cemetery enters, if there are five or more cards in your graveyard, tap enchanted creature.
Enchanted creature doesn't untap during its controller's untap step.

Temporary Lockdown

When Temporary Lockdown enters, exile each nonland permanent with mana value 2 or less until Temporary Lockdown leaves the battlefield.

Sublime Epiphany

Choose one or more —
• Counter target spell.
• Counter target activated or triggered ability.
• Return target nonland permanent to its owner's hand.
• Create a token that's a copy of target creature you control.
• Target player draws a card.

The Master of Keys

Flying
When The Master of Keys enters, put X +1/+1 counters on it and mill twice X cards.
Each enchantment card in your graveyard has escape. The escape cost is equal to the card's mana cost plus exile three other cards from your graveyard. (You may cast cards from your graveyard for their escape cost.)

Azorius Keyrune

{T}: Add {W} or {U}.
{W}{U}: Azorius Keyrune becomes a 2/2 white and blue Bird artifact creature with flying until end of turn.

Orzhov Keyrune

{T}: Add {W} or {B}.
{W}{B}: Orzhov Keyrune becomes a 1/4 white and black Thrull artifact creature with lifelink until end of turn.

Bound by Moonsilver

Enchant creature
Enchanted creature can't attack, block, or transform.
Sacrifice another permanent: Attach Bound by Moonsilver to target creature. Activate only as a sorcery and only once each turn.

Moonsilver Key

{1}, {T}, Sacrifice Moonsilver Key: Search your library for an artifact card with a mana ability or a basic land card, reveal it, put it into your hand, then shuffle.

Petty Theft

Return target nonland permanent an opponent controls to its owner's hand.

Brazen Borrower

Flash
Flying
Brazen Borrower can block only creatures with flying.

Brazen Borrower // Petty Theft

Keys to the House

{1}, {T}, Sacrifice Keys to the House: Search your library for a basic land card, reveal it, put it into your hand, then shuffle.
{3}, {T}, Sacrifice Keys to the House: Lock or unlock a door of target Room you control. Activate only as a sorcery.

Memory Lapse

Counter target spell. If that spell is countered this way, put it on top of its owner's library instead of into that player's graveyard.

Keeper of Keys

When Keeper of Keys enters, you become the monarch.
At the beginning of your upkeep, if you're the monarch, creatures you control can't be blocked this turn.

Dimir Keyrune

{T}: Add {U} or {B}.
{U}{B}: Dimir Keyrune becomes a 2/2 blue and black Horror artifact creature until end of turn and can't be blocked this turn.

Manifold Key

{1}, {T}: Untap another target artifact.
{3}, {T}: Target creature can't be blocked this turn.

Key to the City

{T}, Discard a card: Up to one target creature can't be blocked this turn.
Whenever Key to the City becomes untapped, you may pay {2}. If you do, draw a card.