Quoted By:
>Mega Darkrai
>Dark/Ghost
>Bad Dreams
HP: 70
Attack: 110(20)
Defense: 90(0)
Special Attack: 180(45)
Special Defense: 100(10)
Speed: 150(25)
Making it Dark/Ghost gives it a few key advantages, one being it can avoid Fighting moves and various Normal moves like Extreme Speed. Darkrai also fits various Ghost archetypes already and learns a few Ghost moves so it's not a huge transition.
It would probably gain access to a few more like Hex and Shadow Sneak as well.
>Mega Cresselia
>Psychic/Fairy
>Magic Guard
HP: 120
Attack: 70(0)
Defense: 150(30)
Special Attack: 105(40)
Special Defense: 150(20)
Speed: 95(10)
With Darkrai going Dark/Ghost it would only be fair for Cresselia to also get some goodies. Fairy/Psychic typing and 120/150/150 bulk makes it one of the bulkiest pokemon ever and allows it to fight back against Darkrai with powered up Moonblasts. It was already difficult to KO Cresselia before but now it will be ridiculous.