Unclaimed Territory

As Unclaimed Territory enters, choose a creature type.
{T}: Add {C}.
{T}: Add one mana of any color. Spend this mana only to cast a creature spell of the chosen type.

Ancient Ziggurat

{T}: Add one mana of any color. Spend this mana only to cast a creature spell.

Cavern of Souls

As Cavern of Souls enters, choose a creature type.
{T}: Add {C}.
{T}: Add one mana of any color. Spend this mana only to cast a creature spell of the chosen type, and that spell can't be countered.

Ghostly Changeling

Changeling (This card is every creature type.)
{1}{B}: Ghostly Changeling gets +1/+1 until end of turn.

Johnny, Combo Player

{4}: Search your library for a card, put that card into your hand, then shuffle.

Amoeboid Changeling

Changeling (This card is every creature type.)
{T}: Target creature gains all creature types until end of turn.
{T}: Target creature loses all creature types until end of turn.

Timmy, Power Gamer

{4}: You may put a creature card from your hand onto the battlefield.

Magical Hacker

{U}: Change the text of target spell or permanent by replacing all instances of + with -, and vice versa, until end of turn.

Wastes

Spike, Tournament Grinder

({B/P} can be paid with either {B} or 2 life.)
{B/P}{B/P}{B/P}{B/P}: Reveal a card you own from outside the game that has been banned or restricted in a Constructed format and put it into your hand.

Chameleon Colossus

Changeling (This card is every creature type.)
Protection from black
{2}{G}{G}: Chameleon Colossus gets +X/+X until end of turn, where X is its power.

Collector Protector

{W}, Give an opponent a nonland card you own from outside the game: Prevent the next 1 damage that would be dealt to you or Collector Protector this turn.

Zombie Fanboy

As Zombie Fanboy enters, choose an artist.
Whenever a permanent with art by the chosen artist is put into a graveyard, put two +1/+1 counters on Zombie Fanboy.