These are four NPC crystals that are part of the Gateway to the Deep quest. They are located at 87.6S 4.4W on a a small mountain ledge on the South Direlands Landbridge. The only way to initially access them is through a portal at the end of either the Devatstated Falatacot Temple or the Corrupted Falatacot Temple, both on Aerlinthe. If you speak to Shemza before handing the Yellow Jewel you'll be flagged to use the the portal just west of Ayan Baqur at 60.3S 90.7W that takes you directly to the Gatekeepers (useful for returning once a week to loot the Black Marrow Reliquary chests).
Shemza
Shemza tells you, "A warrior! A warrior comes! Brothers, feast your eyes on one who would give their lives willingly to the great lord!"
Shemza tells you, "You seek to bask in the glory of Grael, do you not? You seek to join us in the worship of he who is more powerful, more glorious, than all who have come before? My brothers and I, we were the first to join his side. We were there when he led us to victory over the old ones. We helped him slay the mages and lay waste to their cities. We were there when he led an army upon the heretics of the light."
Shemza tells you, "When defeat fell upon us, we knew that our ascendance was only delayed. One day, we knew that our god would rise from the depths and claim that which is his. And we knew that ones such as you would seek to free him from his chains."
Shemza tells you, "And now you are here. You seek to barter with us who have given our souls in exchange for life eternal. Those of us who have lengthened our lives for the sole purpose of delivering warriors unto him."
Shemza tells you, "Yes. You are here now. And now you will aid me. And then you will aid my brothers."
Shemza tells you, "I seek a boon. One small boon. The masters of the portal carry a token of golden hue. A token that I would claim as mine own. Find it and deliver it to me. Then the first part of your quest shall begin."
Shemza tells you, "I have altered your body. You may now use our portal near Ayan Baqur."
Lurza
Lurza tells you, "You must bring to me a shard of the Radiant Crystal. Only when Shemza sings your name to the lord of the deep will you gain access to that Crystal."
Dmesne
Dmesne tells you, "I require a shard of the Dazzling Crystal. Until you have acquired one of these from my brother Lurza, I will have naught to do with you, little one."
Rhujun
Rhujun tells you, "A shard of the Brilliant Crystal is all I require. Until I have it, you are not fit."
