The Fidelius Charm

When The Fidelius Charm enters the battlefield,
roll a D20. Place X secrecy counters equal to the
die roll on The Fidelius Charm.
At the beginning of your opponents combat step,
that opponent rolls a D20. If they roll a number
less than the number of secrecy counters,
creatures that opponent controls cannot attack
you or planeswalkers you control.
At the beginning of your upkeep, remove a
secrecy counter.