“Once socketed, a legendary upgrade has the power to take on the properties of any other upgrade of its type. You can freely socket and remove them from any type of armor without using an Upgrade Extractor. Unlike other legendary items, legendary upgrades have no visual effects. Legendary runes provide the same set bonuses as other runes, and you can combine them with exotic superior runes. For example, if you have a Superior Rune of the Adventurer in your helm, and you add a legendary rune to your boots, setting the legendary rune’s suffix to Adventurer will grant the two-piece bonus for that set.”
Starting next week on July 30th, players will be tasked with donating multiple items and turning in gobs of lucent crystals in exchange for satchels of loot to “force” the Mystic Toilet to poop out the knowledge for these runes. “Every donation progresses a global community goal,” ArenaNet says. “Once the goal is complete, the ability to create new materials for legendary upgrades will become available to every discipline that can craft upgrades.”
Reddit’s reaction is quite mixed, as players debate the proposed UI for the mechanic, the lucent crystal economic outlook, and whether or not the overall playerbase will get much use out of the system.
— Guild Wars 2 (@GuildWars2) July 24, 2019