msem-instigator

Crumbling Aqueduct enters tapped unless you control another Desert.
{T}: Add {U} or {B}.

Crumbling Necropolis enters tapped.
{T}: Add {U}, {B}, or {R}.

({T}: Add {B} or {R}.)
Whenever Crumbling Precipice becomes tapped, you lose 1 life unless you control two or more basic lands.

Crumbling Shrine enters tapped. When it does, it explores. (Reveal the top card of your library. Put that card into your hand if it's a land. Otherwise, put a +1/+1 counter on this, then you may put that card into your graveyard.)
{T}: Add {G}.
{2}{G}{G}: Crumbling Shrine becomes a Nymph creature. (This effect lasts indefinitely.)

Crumbling Vestige enters tapped.
When Crumbling Vestige enters, add one mana of any color.
{T}: Add {C}.

{T}: Add {C}.
{X}: Crypt of Myriad Fates becomes a copy of target creature card with mana value X or less in your graveyard until end of turn, except it's 2/2 and a land in addition to its other types. Activate only outside of combat.

Puzzlebox (Begin the game with this and another card you own from outside the game in the command zone, locked. That card is face down until you unlock this.)
{1}, Discard two cards: Unlock Cryptic Fragment. If the revealed card is a basic land card, put it into your hand.

Cryptic Reef enters tapped.
{T}: Add {G} or {U}.
{2}{G}{U}, {T}, Sacrifice Cryptic Reef: Draw a card.

({T}: Add {U} or {R}.)
Whenever Crystal Cavern becomes tapped, you lose 1 life unless you control two or more basic lands.

Crystal Garden enters tapped.
{T}: Add one mana of any color. You can't spend this mana to cast a creature spell.

{T}: Add {C}.
{T}, Pay 1 life: Add {U} or {B}.

{T}: Add {C}.
{T}, Pay 1 life: Add {W} or {U}.

You may look at the top card of your library.
{T}: You may play the top card of your library.

Enchant player
At the beginning of enchanted player's upkeep, that player upgrades a creature you control. (They give it one of the listed counters it doesn't have.)
• +1/+1
• Lifelink
• Menace

({T}: Add {W} or {B}.)
Cursed Wastes enters tapped.
{1}, {T}: Add {W}{W} or {B}{B}.

CySec Nexus enters tapped.
{T}: Add {W} or {U}.
{W}{U}, {T}: Create a Function token with “Flash.” Activate only as a sorcery. (It's an enchantment. As you cast an instant or sorcery spell, sacrifice any number of Functions to add their effects to that spell.)

Indestructible
Whenever Cyrukan attacks, choose one —
• Create a Treasure token. (It's an artifact with “{T}, Sacrifice this artifact: Add one mana of any color.”)
• Create a Weapon token and attach it to target creature you control. (It's an Equipment artifact with equip {2} and “Equipped creature gets +1/+1.”)
At the beginning of each end step, if you control three or more tokens, transform Cyrukan.

{T}: Add {C}.
{3}{G}: Until end of turn, Damian's Undercity becomes a 2/2 creature. It's still a land. It has lifelink if {W} was spent to activate this ability, gets +0/+3 if {U} was spent, and has deathtouch if {B} was spent.

{T}: Add {C}.
Satrapies you control have “{1}{G}, {T}: Put a +1/+1 counter on target creature. Activate only as a sorcery.”

Danaj Sanctuary enters tapped.
Satrapies you control have “{T}: Add {G} or {U}.”

Danaj Temple enters tapped.
Satrapies you control have “{T}: Add {B} or {G}.”

({T}: Add {R} or {G}.)
As Dangerous Territory enters, you may pay {1}. If you don't, Dangerous Territory enters tapped.

{T}, Sacrifice Daunting Skyline: Search your library for a Plains or Swamp card and put it onto the battlefield tapped, then shuffle.

Dawn Hill Outskirts enters tapped unless you played it from exile.
{T}: Add {R} or {W}.

Dawnlit Battlefield enters tapped.
{T}: Add {R} or {W}.
{2}{R}{W}: Until end of turn, Dawnlit Battlefield becomes a 4/2 red and white Warrior creature with with “This creature has first strike as long as it's attacking” and “Whenever this creature attacks or blocks, torment yourself.” It's still a land. (To torment yourself, lose 3 life unless you discard a card or sacrifice a nonland permanent.)