“Games for the Holidays” promotion features three Xbox LIVE arcade games where you can unlock bonus feature simply by purchasing the games.
The three games part of the promotion include Raskulls, Ilomilo, and A World of Keflings.
Here the bonuses you can unlock and how to obtain them as explained on the press release:
If you purchase all three GFTH titles, extra characters will unlock within the games. For example, you can unlock ilo and Doug as playable characters in Raskulls, and also unlock Raskulls characters within ilomilo and World of Keflings by purchasing the full range of game.
The following games will all be released by December 29th and will be available to download via the Xbox LIVE Marketplace.
