Once your relic weapon novus has been soulglazed by Jalzahn, complete certain activities with the weapon equipped to increase its soul attunement level. By presenting a fully attuned weapon to Jalzahn, you will be rewarded with a relic weapon nexus of item level 115 that retains all the upgrades made to the original relic weapon novus.

A weapon’s soul attunement level will rise by a set amount determined by the activity being performed. This amount, however, may increase each time a certain period of time passes. Thus sharing information with other players will be invaluable in planning the most efficient method of attunement.
Attunement progress can be verified through the use of the Zodiac glass.
You must gain one thousand hugs from one thousand unique players is my guess! Each /hug you receive increases it's love-love points by 1/1000.

Hugs aren't free though, if you want to gain a Nexus weapon, it's 100k per hug. I'm taking advance orders... Get your reservations early!