Incorporated material from Heckna (Hit Point Press), The Wild Beyond the Witchlight, Van Richten’s Guide to Ravenloft, and culminated in Vecna: Eve of Ruin (all Wizards of the Coast/Darrington Press), plus inclusions from Planescape (Sigil and the Outlands), Dark Sun (Mind Lords of the Last Sea), Ravnica (including the Dimir and Izzet), and Eldrazi from Magic: the Gathering.
Status for this project: HotOG is a direct sequel. Events, character fates, and world-state changes from this campaign are canon and count as further ancient history, same as the three CR campaigns — folded into the same 1000-years-later timeline.