Contaminated Ground

Enchant land
Enchanted land is a Swamp.
Whenever enchanted land becomes tapped, its controller loses 2 life.

Mishra's Helix

Gigadrowse

Replicate {U} (When you cast this spell, copy it for each time you paid its replicate cost. You may choose new targets for the copies.)
Tap target permanent.

Psychic Venom

Enchant land
Whenever enchanted land becomes tapped, Psychic Venom deals 2 damage to that land's controller.

Island

Pooling Venom

Enchant land
Whenever enchanted land becomes tapped, its controller loses 2 life.
{3}{B}: Destroy enchanted land.

Slow Motion

Enchant creature
At the beginning of the upkeep of enchanted creature's controller, that player sacrifices that creature unless they pay {2}.
When Slow Motion is put into a graveyard from the battlefield, return Slow Motion to its owner's hand.

Mana Web

Whenever a land an opponent controls is tapped for mana, tap all lands that player controls that could produce any type of mana that land could produce.

Rhystic Study

Whenever an opponent casts a spell, you may draw a card unless that player pays {1}.

Underground Sea

Drift of Phantasms

Defender (This creature can't attack.)
Flying
Transmute {1}{U}{U} ({1}{U}{U}, Discard this card: Search your library for a card with the same mana value as this card, reveal it, put it into your hand, then shuffle. Transmute only as a sorcery.)

Propaganda

Creatures can't attack you unless their controller pays {2} for each creature they control that's attacking you.

Swamp

Drowned Catacomb

Drowned Catacomb enters tapped unless you control an Island or a Swamp.
{T}: Add {U} or {B}.

Mundungu

{T}: Counter target spell unless its controller pays {1} and 1 life.

Copy Enchantment

You may have Copy Enchantment enter as a copy of any enchantment on the battlefield.

Hidden Strings

You may tap or untap target permanent, then you may tap or untap another target permanent.
Cipher (Then you may exile this spell card encoded on a creature you control. Whenever that creature deals combat damage to a player, its controller may cast a copy of the encoded card without paying its mana cost.)