Exploring the Planet
As for where Arthur went after leaving the lab, it was to the planet where the Domain's entrance was located.
Naturally, he teleported to the first hall where the Deity realm golems stood guard before leaving through the door.
The Domain was located in another dimension that had overlapping coordinates with that planet, and since Arthur's current spatial control was not enough for him to jump dimensions, he had to leave through the door like a normal person.
"Come to think of it, Mum was able to break into the Domain with her bare fists. Would I be able to do that when I get to her level or is Mum just an anomaly?"
The boy pondered to himself and thought about his entire family, realising that none of them conformed to what which was established as 'normal' and came to a conclusion.
"High-tier deities probably can't do that normally. Mum's just an irregular."