Board Thread:Question and Answer/@comment-24596086-20150324191911/@comment-887715-20150325162437

Aah, that means there's a requirement you must first fullfillled before you can upgrade the Castle. Here's the details of it:Castle Remember that the area clear requirement there is from the original Chronicle/Celestial Realm 1, not the event one. Don't get confused! You'll also need to level up to specific levels, too. Likewise, it'll naturally go in flow. Try upgrading something else first, like your resource generators and storages(then other buldings you can already start building and upgrading too). You can do that, yes?