Mysterious Artifact

Mysterious Artifact comes into play with
{x} Mystery counters on it.
{2}, Remove a Mystery Counter: Roll a d20
1-8: Gain 2 life
9-16: Create a 1/1 colorless creature token
of a type of your choosing.
17-18: Add 2 Mystery counters to this card
19-20: Tap or untap target perminent.