"Domain As A Nuclear Weapon" 

From the moment the fairy of space summoned the souls of many people in various worlds to enter this world, this world had already opened up itself to various worlds out there, but the tunnel might be scarce. 

Most of the tunnels that appeared would only be tunnels created by the ancestors who went to high-level worlds and as early as when the first transmigrator entered this world, that's when the ancestors found the existence of tunnels, which was a shortcut to leave this world instead of entering the space crack to venture for a long time. 

Entering the space crack to record coordinates and entering the space crack to find a suitable world were two different concepts. 

The first one was less dangerous because these ancestors might have already locked on the location of their favorite world through various records from their predecessors.