When this Case enters the battlefield, search your library for a basic land card, reveal it, put it into your hand, then shuffle.
To solve — There are five colors among permanents you control.
(If unsolved, solve at the beginning of your end step.)
Solved — At the beginning of combat on your turn, target creature you control gains
flying (This creature can't be blocked except by creatures with flying or reach.),
double strike (This creature deals both first-strike and regular combat damage.), and
vigilance (Attacking doesn't cause this creature to tap.) until end of turn.