Given that the distance between Kronos and Mycroft was simply too distant, portals could not be constructed with ordinary spells if not there was no teleportation hub on the scale of the Multiverse Sacrificial Grounds.
"According to the results from four 'Star Observatories', the world of Mycroft is actually very close to the bottom layer of the Abyss."
In a hidden valley in the Kronos Mountains, Barnil was explaining things to Joshua while he controlled the extremely complex runic formations right before him. Around them were hundreds of runic puppets he had summoned, assisting him with repairs on the Observer.
"In fact, circumstances were not exactly identical. But to make an analogy that is easy to understand, the Multiverse is a boundless sphere, while we are located at the bottommost arc, effectively a line's breadth from the Abyss."
