If u searching the mass 278ilvl conduit upgrade item, u requiring the using character to have completed “Souls Entwined” and one of the achivements:
Keystone Hero (All +20’s timed in S3, if u timed all dungs on 20 u achive portals which can u port to all SL Dungeons!)
Elite (2.4k rating in S3)
Kill all Sepulcher of the First Ones bosses on Mythic Difficulty
The Vessel costs 1.2k Gold in at any and only at Renown Quartermaster at urs actual Covenandt.
Reminder if u dont have a Memory / "Legendary" u can buy it at every Quartermaster with the costs of 15 Grateful Offering, instead of u are grinding somewhere else, i know its random but well i think in the actual situation u can do callings.
Or in Korthia u can buy it with 400 Soul Cinders or 1.5k cataloged research. U can buy with 3k Cosmic Flux (where u can farm/grind in Zereth Mortis from rares, treasures and quests) a Box from ZM, where u get the soul ash (5150) and soulcinders(1650). Soul Ash and Cinders can be also farmed in Thorgast in the normal wings and only one time lootable at Jailer's Gauntlet.
Or if u have the anima conductor rank 3 and actived animaways up. Each way costing 30 anima.