I got the cube and picked up everybody and saved. Then I town portaled to Celeste instead of walking out of the cave and brought the cube to Robert (IIRC) when he eradicated me.So reload saved game and was eradicated in the cave by the Coding Wizard
No problem I thought being Autosave saves before you go into a cave, so worst thing would be to just redo the quest and still got eradicated.
So basically I'm eradicated if I go in the cave but he still took the cube and I can't finish the quest or even go back to an ealier saved game