The Three Altars is a side-quest in Divinity: Original Sin 2
You can acquire this quest from finding one of the three altars.
Suggested level: 11-14
Act 2
Walkthrough
It's currently not known what the altars suppose to do. There is also no known way to properly close the quest.
It seems to make a difference depending if you pray with an undead or a living party member.
Journal
Living First
I prayed before an altar, and heard a mysterious, fragmented voice acknowledge me as a Godwoken.
Living Second
I prayed once more at an altar. This time, I heard only the faintest whisper of a voice.
Living Third
I prayed before a third altar, and heard a calm, even voice. It told me that my burden was too great, and implored me to rest. Then it was gone.
Undead Refused First
I prayed before an altar, and heard a mysterious voice. It was calm and benevolent, but did not reveal who it was. As it left, it imbued me with Source power.
Undead Refused Second
I prayed at another altar, and heard the voice once more. Again, I was filled with Source.
Undead Refused Third
I prayed before a third altar, and heard the voice yet again. It seemed to be tempting me, and imbued me with Source once again.
Close Left RC
I set sail from Reaper's Coast. I will learn no more about the altar voice, it seems.