If my experience is anything to go buy, a proxy won't be sufficient. You'll need a Russian VPN. However, given that the key is Russian, there are two further complications you might encounter:
1 - The game will be Russian language only. You will not be able to select any other language (if you speak/read Russian, I guess this won't be a problem for you).
2 - It won't just be the activation of the game that is locked to Russia, but also the ability to play the game. Thus you will need to connect to a Russian VPN each and every time you wish to play the game online -- that could turn out to be damned expensive, unless you can find a free VPN with no bandwidth limitations.