honestly i thought moto implied that the realm crystal was what was keeping the oni out of ninjago like it makes sense the oni had to corrupt it to get there unlike the first realm where they could have shown up where ever and then omega says this about it "The Realm Crystal was merely the key in which we opened the gateway" like its presence in a realm blocks any oni realm travel and thats why the oni had to leave to power up (i guess) so they could have the power to bypass it
Regardless of whether this was the case or not, this actually fits well into my realm crystal lore and thus I am absorbing it *-*)/
















