Video Guide!
This is completed during the Dawntreader Side Quest, which can be started by talking to the man outside the embassy in Paradis.
From there we can follow the quest marker to the Eothasian Temple and make our way through. Don’t worry this is a mostly linear area, where we will eventually meet the Oracle.
During the conversation with the Oracle agree to find the Relic, do not choose any options to antagonize him, and do not mess with the electrical panels near the statue in this room as it will cause him to become hostile.
After that conversation follow the optional objective to grab the relic, then return to the Oracle and choose to activate the statue with the relic as he asks us to do.
After trying the lever only to find it is broken, speak to the Oracle again and choose to put our own soul into the statue. We will be asked multiple times in this conversation if we want to do this, make sure to continue to agree then follow the optional objective until the Oracle kills us and our achievement pops