I am close to finishing the "To Kill an Empire" mission in Skyrim. I learned that after this mission…
…most of the members of the Brotherhood will be slain. Just recently, I learned some info that caught my attention that says "Subsequently, Gabriella is killed during the Penitus Oculatus assault on the Dark Brotherhood Sanctuary (You can extract her blood using Essence Extractor for Discerning the Transmundane quest). Her corpse can be found on the table where Festus Krex, Babette, and herself usually stayed."
Reference: http://elderscrolls.wikia.com/wiki/Gabriella
It got me thinking that should I postpone finishing this quest until after I complete the "Discerning the Transmundane" mission? Is there any implication or negative effect if I finish the Brotherhood mission before I obtain the Essence Extractor?
Best Answer
For the quest, Discerning the Transmundane, you need to extract the blood of one of each of the elvish races (Altmer, Dunmer, Orsimir, Falmer, Bosmer) - the note in the wiki is just to alert the player that Gabriella's blood can be extracted to fulfill the requirement of Dunmer blood.
You can harvest Dunmer blood from any dark elf in the game. It does not have to be Gabriella.