Y'Sidra, Gaol Wanderer

Flash
Deathtouch
Anticipation—{1}{b}{b}, reveal Y'Sidra, Gaol
Wanderer from your hand. When you do, put a containment counter on target permanent.
When Y'Sidra, Gaol Wanderer enters the battlefield, create X token copies of the card
Ghostly Prison. Where X is equal to the number
of containment counters on permanents.