They don't "have" to do anything, It's not as if you own your account, and even if you did you can not sue them for something that is out of their control.
But, like I said, if you are suggesting they become beings of a higher power in order to provide you with access to a server their host isn't capable of putting online at the moment, I'm sure a Judge would agree.
That is literally the only course of immediate action they could take to provide you with the service you payed for without reading the contract. (I can only assume you didn't read it based on your sense of being owed)
EDIT: I feel as though I should clarify how Evony works in terms of what you pay for.
You don't pay for access to the account. That is free. You pay for cents, an in-game currency. Being as the account is free, Evony owns the account. You do not. You don't own the cents you pay for either, You "rent" them. You may use them while Evony chooses to let you use that account. If at any point (and for almost any reason) Evony decides you don't get to use the account anymore, they take it. Good luck suing them for denying you access to something that belongs to them.
Read the ToS.. It is a contract, it is legally binding. The terms and service of any video games are contracts. They are written by lawyers, Evony is a business.
You will get laughed at if you take them to court. They have VERY good lawyers, I've seen them in action, as have any of the other players who have been around since the beginning.

