Thanks to TheSilentGrovyle for suggesting this mega.

As if the god pokemon was not powerful enough already, I've thought of a mega evolution for it. Arceus gets Divine empowerment, which has a 10% chance of raising all of Mega Arcueses stats each turn. It gets a overall stat boost making its stats rest at 140 each. Its appearance changes to be that it gets bigger and gets another ring around its body. It floats in the air now, overflowing with divine power and overwhelming aura.
Stat boosts:
20 attack
20 sp attack
20 defense
20 sp defense
20 speed