GF said it wasn't DNA in an interview, it a reference to XYZ axis on a cartesian plane, First 3D game and all.
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And their designs are based on norse gods,
The eagle who lives in the branches of Yggdrasil
The deer that guards the trunk
The serpent that chews at the roots.
Next legendary will probably be a squirrel of some sort (to the right of the deer), to represent Ratatosk, the squirrel that runs.
Or a snake to represent Jörmungandr, the snake at the edge of the world.