I came here, via Google Search, to enquire this very thing. I was explicitly given the ‘choice’ to seek out Donan, before continuing with the main quest, should I wish to. (I cannot remember the dialog as it was over an hour earlier, but having picked up a side quest in that direction, I remembered having just been given the ‘choice’ and opted to do just that.)
There needs to be a ‘check’ to see if that Quest Stage has been reached before showing that particular dialog option, as I just had a major spoiler revealed and was scratching my head in puzzlement at who this Rathma was; why did he **** his ***? Why was he seeking a certain thing and how did Lilith get her hands on it? It was, no… it IS, no small thing to drop a lore bomb like this on an unsuspecting player.