Is Atlantica game free to play? I think they will do it free, they’ll just have like premium items where players can increase the Stamina for more play or equipments for stronger characters.

Yep, it's free to play and they have the item mall wherein you can buy stuffs that can be very useful in the game. I'm earning in game money now  so that I can buy items that the players buy from the item mall and sell it in game :) work work work!