Dr, Ellen Mindreader

At the beginning of your upkeep, choose target opponent. Until end of turn, that player can't
cast spells, you may look at the top card of their
library any time, you may play the top card of
their library, and you may spend mana as though
it were mana of any color to cast spells this way.
Instant and sorcery spells you cast this way
have demonstrate