Ruby, Accursed DemonFox

{x}{b/r}{b/r}{t}:Gain control of target creature with
cost {x} or less another player controls for this
turn. If this creature is tapped, untap it.
{x}{b/r}{b/r}:Ruby, Accursed DemonFox becomes
a copy of target creature with this ability.
Activate only as a sorcery and once per turn.
Her powers of seduction and shapeshifting are
unmatched among her kind, making her a
deadly opponent.