Have

Scatter Ray

Counter target artifact or creature spell unless its controller pays {4}.

Essence Scatter

Reasonable Doubt

Counter target spell unless its controller pays {2}.
Suspect up to one target creature. (A suspected creature has menace and can't block.)

Three Steps Ahead

Spree (Choose one or more additional costs.)
+ {1}{U} — Counter target spell.
+ {3} — Create a token that's a copy of target artifact or creature you control.
+ {2} — Draw two cards, then discard a card.

Deduce

Draw a card. Investigate. (Create a Clue token. It's an artifact with "{2}, Sacrifice this artifact: Draw a card.")

Sword of Once and Future

Equipped creature gets +2/+2 and has protection from blue and from black.
Whenever equipped creature deals combat damage to a player, surveil 2. Then you may cast an instant or sorcery spell with mana value 2 or less from your graveyard without paying its mana cost. If that spell would be put into your graveyard, exile it instead.
Equip {2}

Haughty Djinn

Flying
Haughty Djinn's power is equal to the number of instant and sorcery cards in your graveyard.
Instant and sorcery spells you cast cost {1} less to cast.

Island

Eluge, the Shoreless Sea

Eluge's power and toughness are each equal to the number of Islands you control.
Whenever Eluge enters or attacks, put a flood counter on target land. It's an Island in addition to its other types for as long as it has a flood counter on it.
The first instant or sorcery spell you cast each turn costs {U} (or {1}) less to cast for each land you control with a flood counter on it.

Flow of Knowledge

Draw a card for each Island you control, then discard two cards.

Change the Equation

Choose one —
• Counter target spell with mana value 2 or less.
• Counter target red or green spell with mana value 6 or less.

Disdainful Stroke

Counter target spell with mana value 4 or greater.

proxied

Demolition Field

{T}: Add {C}.
{2}, {T}, Sacrifice Demolition Field: Destroy target nonbasic land an opponent controls. That land's controller may search their library for a basic land card, put it onto the battlefield, then shuffle. You may search your library for a basic land card, put it onto the battlefield, then shuffle.

Negate

Moment of Truth

Look at the top three cards of your library. Put one of those cards into your hand, one into your graveyard, and one on the bottom of your library.

Tolarian Terror

This spell costs {1} less to cast for each instant and sorcery card in your graveyard.
Ward {2} (Whenever this creature becomes the target of a spell or ability an opponent controls, counter it unless that player pays {2}.)

Run Away Together

Choose two target creatures controlled by different players. Return those creatures to their owners' hands.

Phantom Interference

Spree (Choose one or more additional costs.)
+ {3} — Create a 2/2 white Spirit creature token with flying.
+ {1} — Counter target spell unless its controller pays {2}.

Sleight of Hand

Look at the top two cards of your library. Put one of them into your hand and the other on the bottom of your library.