River Song

Meet in Reverse — You draw cards from the bottom of your library rather than the top.
Spoilers — Whenever an opponent scries, surveils, or searches their library, put a +1/+1 counter on River Song. Then River Song deals damage to that player equal to its power.

Magmatic Hellkite

Flying
When this creature enters, destroy target nonbasic land an opponent controls. Its controller searches their library for a basic land card, puts it onto the battlefield tapped with a stun counter on it, then shuffles. (If a permanent with a stun counter would become untapped, remove one from it instead.)

Experimental Augury

Look at the top three cards of your library. Put one of them into your hand and the rest on the bottom of your library in any order. Proliferate. (Choose any number of permanents and/or players, then give each another counter of each kind already there.)

Return the Favor

Spree (Choose one or more additional costs.)
+ {1} — Copy target instant spell, sorcery spell, activated ability, or triggered ability. You may choose new targets for the copy.
+ {1} — Change the target of target spell or ability with a single target.

Lutri, the Spellchaser

Companion — Each nonland card in your starting deck has a different name. (If this card is your chosen companion, you may put it into your hand from outside the game for {3} as a sorcery.)
Flash
When Lutri enters, if you cast it, copy target instant or sorcery spell you control. You may choose new targets for the copy.

Cleansing Wildfire

Destroy target land. Its controller may search their library for a basic land card, put it onto the battlefield tapped, then shuffle.
Draw a card.

Volatile Fault

{T}: Add {C}.
{1}, {T}, Sacrifice this land: Destroy target nonbasic land an opponent controls. That player may search their library for a basic land card, put it onto the battlefield, then shuffle. You create a Treasure token.

Krenko's Buzzcrusher

Flying, trample
When this creature enters, for each player, destroy up to one nonbasic land that player controls. For each land destroyed this way, its controller may search their library for a basic land card, put it onto the battlefield tapped, then shuffle.

Field of Ruin

{T}: Add {C}.
{2}, {T}, Sacrifice this land: Destroy target nonbasic land an opponent controls. Each player searches their library for a basic land card, puts it onto the battlefield, then shuffles.

Ghost Quarter

{T}: Add {C}.
{T}, Sacrifice this land: Destroy target land. Its controller may search their library for a basic land card, put it onto the battlefield, then shuffle.

Radiant Performer

Flash
When this creature enters, if you cast it from your hand, choose target spell or ability that targets only a single permanent or player. Copy that spell or ability for each other permanent or player the spell or ability could target. Each copy targets a different one of those permanents and players.

Dualcaster Mage

Flash
When this creature enters, copy target instant or sorcery spell. You may choose new targets for the copy.