Fiona, Narcoleptic Companion

When this creature enters the battlefield, choose another creature you control. Fiona, Narcoleptic Companion becomes bonded with this creature. When another creature enters the battlefield under your control, if this creature isn't bonded you may have that creature bond with Fiona.
Fiona must attack and block with the creature she is bonded with. The bonded creature gets +3+3 and if Fiona attacks with the bonded creature, she gains hexproof and can't be blocked.