Counterspell

Isochron Scepter

Imprint — When Isochron Scepter enters, you may exile an instant card with mana value 2 or less from your hand.
{2}, {T}: You may copy the exiled card. If you do, you may cast the copy without paying its mana cost.

Island

Twincast

Copy target instant or sorcery spell. You may choose new targets for the copy.

Withdraw

Return target creature to its owner's hand. Then return another target creature to its owner's hand unless its controller pays {1}.

Mystic Sanctuary

({T}: Add {U}.)
Mystic Sanctuary enters tapped unless you control three or more other Islands.
When Mystic Sanctuary enters untapped, you may put target instant or sorcery card from your graveyard on top of your library.

Mana Leak

Counter target spell unless its controller pays {3}.

Archive Trap

If an opponent searched their library this turn, you may pay {0} rather than pay this spell's mana cost.
Target opponent mills thirteen cards.

Boomerang

Return target permanent to its owner's hand.

Shelldock Isle

Hideaway 4 (When this land enters, look at the top four cards of your library, exile one face down, then put the rest on the bottom in a random order.)
Shelldock Isle enters tapped.
{T}: Add {U}.
{U}, {T}: You may play the exiled card without paying its mana cost if a library has twenty or fewer cards in it.

Increasing Confusion

Target player mills X cards. If this spell was cast from a graveyard, that player mills twice that many cards instead.
Flashback {X}{U} (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Reality Shift

Exile target creature. Its controller manifests the top card of their library. (That player puts the top card of their library onto the battlefield face down as a 2/2 creature. If it's a creature card, it can be turned face up any time for its mana cost.)

Visions of Beyond

Draw a card. If a graveyard has twenty or more cards in it, draw three cards instead.

Jace, Memory Adept

+1: Draw a card. Target player mills a card.
0: Target player mills ten cards.
−7: Any number of target players each draw twenty cards.

Accumulated Knowledge

Draw a card, then draw cards equal to the number of cards named Accumulated Knowledge in all graveyards.

Ghost Quarter

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