There are a lot of theories going around as to what the significance is behind Pokémon X and Y Versions’ names and the designs of the two featured Pokémon. At this point, we’re all aware that X, Y, and Z are the axes of a three-dimensional plane, fitting for Pokémon‘s first main-series foray onto Nintendo 3DS. But everything we’ve seen about the design of these creatures is far too intricate to be so shallow.

A user on Tumblr featured by Kotaku seems to think they allude to the endoderm, ectoderm, and mesoderm, the types of cell formations from which animals develop, but offers little explanation. Laura from KimikoGaming, on the other hand, has a bit more defendable of a point: Pokémon X and Y Versions are based on Norse mythology. Not Thor and Loki the way Marvel depicts them, but the original beliefs held by the Germanic peoples who looked to the skies and saw the land of Asgard.

In Norse mythology, the Tree of the World, Yggdrasil, is located at the center of the universe and holds the nine worlds together through its roots. While X, Y, and Z represent the three axes on a 3D plane, they also represent the three encompassing realms held by Yggdrasil: Asgard, Midgard, and Niflheim. Each of the nine worlds held by these realms is home to a different race and is located in a different area of the tree. Most importantly, each of the three encompassing realms is represented by a different animal.

Asgard, home to the gods, is the first of these worlds. Asgard is located at the top of Yggdrasil, also home to a divine eagle. This eagle is said to be blind, but graced with the ability to see into the souls of all Yggdrasil’s creatures from all nine realms. The majestic Yveltal reminds us of this eagle due to its avian features and “legendary” powers. Furthermore, as people and animals go blind, their eyes tend to develop a tinge of blue. Yveltal’s eyes are a shocking light blue, as seen in the game’s trailer, implying that it may be blind and/or have the ability to see into the souls of people and Pokémon.

Descending Yggdrasil, the next world we encounter is Midgard, the world of the mortals. Midgard is home to four stags with branch-shaped horns as high as Yggdrasil itself. Each of these four stags houses a different-colored jewel in its horns—red, blue, yellow, and purple. As we can see between the two official depictions of Xerneas, the creature has all four of these colors inside its tall, branch-shaped horns, which would appear to represent all four mythical stags in one.

But the roots of Yggdrasil are certainly the most interesting to this theory, especially in the context of understanding the story of Generation VI. The roots of Yggdrasil hold together the remaining seven realms, and along those roots slithers a serpent-like dragon, trapped by the tree’s roots from the rest of the universe. This dragon, Niohoggr, gnaws on the roots of Yggdrasil as it crawls across Niflheim, the land which houses Hel, Realm of the Dead. Could the third Pokémon in this new legendary trio be a serpent coiling its body in the shape of a Z? Much like how Yveltal and Xerneas represent concepts akin to Heaven and Earth, could this mysterious third Pokémon represent Hell?

What’s also intriguing about this theory is how well it ties into the already understood ideas of the 3D plane. Yveltal of Asgard represents the Y-axis through its large wings and gift of flight. Meanwhile, Xerneas of Midgard is restricted to the ground by its lack of wings, forced only to walk horizontally the surface of the Earth, or the X-axis, if you will. The third Pokémon, based on Niohoggr, can be assumed to crawl back and forth across the roots of this tree, which spread in all directions. Much like how the Z-axis can be placed anywhere among the X and Y axes to form a 3D plane, the roots of Yggdrasil are not bound by a constant height.

There was a scene in the official trailer showing the game’s protagonist swinging from rope to rope high in a large tree, as pictured to the left. This could always be a Grass-type Gym, but is it also possible that this tree is the home to X and Y‘s legendary Pokémon, much like Spear Pillar or Dragonspiral Tower?

Is this theory ludicrous, or is it all too coincidental to ignore? Would you be excited to see a serpent as the third legendary Pokémon in the potential Z Version?