Serini and her Sidekick

[Mad Humanist]

The Crystal golem was purple, not green, so I'm not so sure of that.

I don't follow your logic here. It never occurred to me that Grubwiggler may have done Serini's half-golem work. But now you mention it I think that is entirely possible.

I am guessing that your thinking is that each golem creator creates golems with a different colour speech bubble. I think it is far more likely that the colour of the speech bubble tells you the golem type. So presumably Crystal had purple because she was a flesh golem. Presumably Serini has green because she is an iron half-golem. And the orange voice has orange because he is a clay golem. So no living beings were harmed in his making.

So the argument that it is Grubwiggler is conservation of detail. Maybe that suggests that the Serini/Xykon meeting was in Greysky City.

This would imply that the whole Celia/Grubwiggler arc was a sort of foreshadowing of the reveal about a Serini/Grubwiggler interaction.