Death goes on to pave the way for life so that isn't necessarily satanic.
The devil on the other hand is an angel fallen from the grace of god, sealed to his own personal dimension as he tries to resist the ways of his former Father.
Giratina was restricted to his own dimension, the distorted world, after being too destructive. Furthermore, it is known as the renegade pokemon. You seeing the similarities.
The typing can draw vague connections too, Ghost cuz of the occult and link to the afterlife. Dragon because it falls to Ice (Fire/Ice, ice goes against hell, though that one is a stretch and a half) and dragon also falls to holy fairy types now, so even more connections.
Yveltal is just a dick.