Threshold Nexus

Upon the casting of this spell, designate a number of creatures to be operators of this nexus.  You imbue the crystal component with magical energy to allow it to anchor a threshold network.  By focusing on it for 1 minute, you or an operator can magically break off a small piece of it.  This small piece of crystal can be used as the material component for the Link Threshold spell. 

You or an operator, by focusing on the nexus for 1 minute,  become aware of all linked doorways and their passwords.  You may sever any number of these doorways or change any number of these passwords while focusing on the crystal.  A password can be verbal or somatic.

The crystal has 500 hit points, an AC of 15, resistance to all damage except thunder, immunity to poison and psychic damage, and immunity to all conditions.  It regains 1 hit point per minute and breaking a piece off as part of this spell deals 50 damage to it.  If the crystal is reduced to 0 hit points, the network is destroyed.  

By spending 1 hour concentrating on the crystal, you may designate new operators or remove previous ones.  If you die, the nexus is left owner less, after which one of the operators may claim ownership of it by casting this spell on the crystal.  Doing this keeps the threshold network in tact.  However, each day that the nexus has no owner, there is a cumulative 5% chance of a random doorway's connection being lost.

If the threshold network is destroyed, all doorways linked to the network lose their link to the network.  Any portals linked through this network that are created by the Threshold spell immediately close.