You will need to start this long-ass quest chain. The last quest is "Heading to Epheria" not "To Epheria" (check prerequisites for the 1st quest - Injured Explorer):

http://bdocodex.com/ru/quest/690/1/

В Хиделе нужно выбрать и пройти 1ю ветку заданий([Выбор I] Молодой лев Хиделя).
После завершения задания Реликвия башни Трины
Вызвать черного духа и прянять квест Эферия: Те, кто уходят
У Алустина в Эферии нужно выбрать Куда ушли путники Эдана
после чего получите данное знание.

This one is long. Play through the Balenos main questline. Once you get into the Serendia questline you will hit a Crossroads. Select the first one [The Lamenting Head of the League of Merchants]. After that, play through the whole Serendia questline and work your way through the Calpheon questline. Near the end of it you will do the quest Relic of Trina Beacon Towers. After you complete that quest, talk to black spirit and he will give you the quest [Port Epheria] Those Who Are Leaving. MAKE SURE YOU HAVE ALL QUEST TYPES SELECTED OR IT WON'T SHOW UP. Once you get to Epheria, talk to Alustin for the quest and select the first option to obtain the knowledge.

解主線 --- 在賽林迪亞主線中分支選第一個 [選擇]商人會長的苦衷 ，接著一直解到卡爾佩恩主線其中的 特里娜烽火台的文物 任務之後，黑精靈會有一個任務叫 [艾裴莉雅]離開的人們 ，接那個支線任務去艾裴莉雅和 艾羅斯汀 對話，選第一個選項「艾丹一行人都去哪裡了？」即可獲得這個知識。