(SPOILER)During the time when Sandoria went vs the Orcs in the war, they were in a big disadvantage. So in order to save their city, they gave away a sword of power(forgot the name) to Tavnazia to draw the beastmen away and thats why you see tons of Orc artilery and soilders. As it can be seen the city fell and Aldo fled with the sacrifice of his sister. Aldo resides in the Tenshodo area of Jeuno. And hence Tavnazia is just the sacrifice to make Sandoria live into this current state from Orc invasion..

With the introduction of CoP, Tavnazia is an accessible area that is open once you beat the 3 Promyvions. It is a real town with a AH that links to Jeuno.