Given my recent posting that shows Soontill appears to have been cover for the fact Raxxla was Guardian in origin, we now have a considerably limited search zone (as opposed to whole galaxy). This also narrows the search zones down rather considerably. We can now utilize Codex Map to locate Guardian locations which include the following:
Inner Orion Spur (nearest Guardian sites)
Inner Scutum-Centaurus Arm
Norma Expanse
Hawking's Gap (suspected)
Outer Orion Spur
Temple
Empyrean Straits
Elysian Shore (suspected but only Thargoids confirmed)
Sanguineous Rim (suspected but only Thargoids confirmed)
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If I had to guess Empyrean Straits near the core would be my guess given the globular clusters near the core of the galaxy. We already know where the edges of the Guardian sites are given the Codex Map rumors.
Inner Orion Spur (nearest Guardian sites)
Inner Scutum-Centaurus Arm
Norma Expanse
Hawking's Gap (suspected)
Outer Orion Spur
Temple
Empyrean Straits
Elysian Shore (suspected but only Thargoids confirmed)
Sanguineous Rim (suspected but only Thargoids confirmed)
---
If I had to guess Empyrean Straits near the core would be my guess given the globular clusters near the core of the galaxy. We already know where the edges of the Guardian sites are given the Codex Map rumors.