Serpent of Slytherin

When Serpent of Slytherin enters the battlefield or transforms, Petrify 3 (Target creature gets three petrify counters on it. At the beginning of its controller's upkeep, remove a petrify counter from it. As long as a creature
has a petrify counter on it, it loses all abilities
and cannot attack or block.)
{2}{b}{b}{t}: Transform Serpent of Slytherin.