Hello! So for my sources, I extrapolate information from the game itself (item descriptions, dialogue, environmental details, etc.), various lore videos (such as Smoughtown, Hawkshaw, Brothers Code, Zulia the Witch, etc.) and the unofficial timeline created and used by several lore Youtubers. Typically I use the lore videos as a rough guide, using them to help understand broader themes/information I might have missed, though I don’t take them as gospel (as seen with conflicting information and interpretations of loretubers I.e. Smoghtowns interpretation of Marika Vs. Fatbrett’s interpretation). Because of that conflicting information I typically go with what I can extrapolate from the game itself. Though I will say that for certain topics, such as Marika and Radagon’s role in the rise and decline of the Lands Between, I do often find myself agreeing with most of FatBrett’s interpretations and extrapolations, especially regarding the Shattering.
I also recommend watching Hawkshaw’s color theory, as color of objects, items and spells/incantations has a major role in the storytelling of the game.