Significance of similar leitmotifs in Shinryu and Fractal Continuum themes?

[Jonnycbad]

Fractal https://youtu.be/8EaPDO6pPuE?t=59
Shinryu: https://youtu.be/qAHFZR0D9ss?t=50 and https://youtu.be/qAHFZR0D9ss?t=122
https://youtu.be/dYOSYDBJyZg?t=56
Axys Lla: https://youtu.be/dYOSYDBJyZg?t=56

Is it just an Allagan theme?

[ChaoticCrimson]

Yeah, that portion first appears in Azyz Lla's field theme (Order Yet Undeciphered). It reoccurs in Unbreakable (Fractal's theme), Heroes Never Die (Thordan Ex first phase, a battle which is set in Azyz Lla), and then in Scale and Steel (The variation of The Worm's Head that plays when Shinryu first appears alongside Omega, which was then considered to be some sort of Allagan construct before we delved deeper into it's background). So in short, yes that leitmotif seems to be in reference to Allagan-related locations and such. The fact The Worm's Head was rearranged as a battle loop for Shinryu's first phase at the end of 4.0 was likely just in reference to it's introduction scene.

[ObsidianFire]

You also here the "Allagan Theme" in "He Who Continues The Assault". It's Regulus' battle theme.

[Jonnycbad]

I thought I heard it during the first part of Zurvan's theme after his Ultimate as well...

[ChaoticCrimson]

You also here the "Allagan Theme" in "He Who Continues The Assault". It's Regulus' battle theme.

Oh yeah, how could I forget that one?