Mercurial Emergence

Whenever an opponent casts a creature spell, create an x/x Mercurial Mimic creature token, where x is the converted mana cost of that spell.
{x}{x}{x}{b}{b}{b}: Create x x/x Mercurial Mimic creature tokens, where x is the amount of Mercurial Mimic creature tokens you control.
{x}{x}{x}{x}{x}{b}{b}{b}{b}{b}: Create x x/x Mercurial Mimic creature tokens, then target opponent loses life equal to the amount of Mercurial Mimic creature tokens you control.