User blog comment:EpicBananaMan/i dont know wat to do :(/@comment-23264387-20140126144104

I think it should say this

OK, I've beaten the WoF, went to the corruption and destroyed almost all of the demon altars. I didn't see a message pop up saying that I had received mithril ore, so is there a way for me to get more demon altars or mithril ore?

Oh, and as for your question no you cannot obtain mithril legitimatly at this point. To get more demon altars you must either use World Edit or cheat them into your inventory, and to get mithril you must create a new world and repeat the process or cheat it into your inventory.