One thing to note is that it has been technically inaccessible to everyone in the Vesspyr Isles. The Nexus Core entrance is in the Ethernere but apparently it pierces the veil and the dead can not enter it. This makes the Nexus Core very secure since only the dead can accidently find the entrance since they can't use it. The only being that could access the Nexus Core was Drinal...until the true spirit helped us to create a breach into the Ethernere. Now there are lots of living beings wandering the Ethernere and the defenses have been tested.