Unlocking Clan Lore
You need to go talk to Custos, Maia, Kirill, Omnis and Em frequently to gradually unlock all the clan lore. I suggest you go talk to them after every match, and over time all the lore will be unlocked.
There is no set order in which to unlock – just keep talking to them.
Also, keep in mind the Senechal lore entry cannot be unlocked. Someone put it in the menus a bit too early and there is no lore in the game to unlock for this particular entry.