Bjoris, Frostcaller Druid

When Bjoris, Frostcaller Druid entres the battlefield, put two +1/1 counters on target
snow creature you control.
{s}{s}{s}{s}, {t}: Create a Legendary 3/2 blue and
green Elemental snow creature token named Frostmane. It has: "{ut}, Add X colorless mana,
where X is this creature's power".