The Battlespire exists in the time of ESO. I hadn't seen this confirmed before. I don't know if there's any lore about the Battlespire's founding but, if there is I've never seen it.
There was definitely a mention of Battlespire in ESO or at least in loremaster's archive series with Lawrence as far as I remember. Nice to see it mentioned again, giving some hope for some bit more "obscure" lore incoming.