Originally Posted by Assaundrell Yumerai
Well, the only way to get Darkrai without any devices is by getting a Japanese version game. (Yep, see my thread about it) anyways, getting both Darkrai and Shaymin on those Japanese versions was dangerous.
Update your info, darkrais have been legit without tweaking for almost a year. As previously mentioned, they can be obtained via the new ranger game as well as by attending the 10th movie in japan. Thousands of people went to that event so there's a lot of them floating around sites like this.
Your best bet at gaining something of equal value to an event pokemon is by chaining a shiny pokemon, guides on how to do this can be found on sites like serebii. Very few people will be willing to trade a non-competetive palkia for a relatively rare event pokemon, since many people put them in the GTS in exchange for things in the national dex as simple as heracross.