Characters that were created as part of any past season of the DUNGEONS & DRAGONS Encounters (DDE) program can be converted into LFR characters to continue their adventures. DDE characters may not be converted to LFR characters until after the end of the entire DDE season in which the character played. DDE adventures can never be played for LFR credit (even under the My Realms program). Amusingly enough, this immediately caused problems with my PC for Crystal Cave, as the reward he got from the finale was beyond the scope of the LFR campaign (a level 9 alternate reward), but yeah. Any past season. Including Dark Sun (there are some caveats about things you have to change, of course, such as deities and the like).