>>13821777There was a guy claiming the three different axis when viewing something in 3d were X for lateral movement, Y for height and Z for depth, and therefore Xerneas walks the ground, Yveltal flies and Z would burrow.
In norse mythology, the tree of life, Yggdrasil, also has a blue-eyed bird at its top, four different-colored-antler stags with twisted horns at the base, and a corpse-scavenging worm-snake at the bottom.
Combine this with poison being SE on fairy and dark being SE on ghost, and the letter Z could find no better animal to represent it than a snake IMO, and we have ourselves a highly speculative gengar snake legend to dominate all metagames with sludge bomb and shadow ball.
It also does a neat little balance among X, Y and Z, with X>Y>Z>X
We can only believe.
on-topic, I prefer Yveltal, not only because it will be able to learn fly, replacing whatever bird I carry, but also due to the solid blue eyes and imposing figure, with the mane and all. 
