I have a doubt about volcarona(black 2 / white 2). We know that he isn't a legendary Pokemon. But why when I encounter it at relic castle, it is showing as 'Volcarona appeared!' instead of displaying ' A wild Volcarona appeared!' ?
This is because Volcarona is a Static Encounter. This means that it'll appear and attack you in the overworld in Relic Castle. There is only one, so you can battle it before OR after defeating E4.