David, Perceptive Apprentice

When David enters the battlefield, choose
an opponent to become your mentor.
Whenever your mentor casts a non-creature spell,
draw a card.
Whenever a creature enters the battlefield under
your mentor's control, create an observer token.
Whenever you cast a spell, your mentor creates a treasure token.
{b}{b}{u}{u}, {t}: Until end of turn, up to three observers gain an ability of a card in your mentor's graveyard.