Gah! Well that was rather ill timing. :| I just made the post of my character heading to the Sepulchre.
I suppose you could have your character catching up with the Lynn and Ewan because she decided on the last minute (quite literally in real life) that she wanted to go anyway.
The mission is pretty straightforward. Lynn & co. are heading into an abandoned burial place where a bad pokémon is hiding an item stolen from an Alakazam, and it's up for the rescue team to retrieve the item. Of course, hiding in the ruins are ghost pokémon.
If you haven't a clue how or what you want to post, I'd recommend reading how other people do it and thinking up filler surrounding your character's history, and tying that into the actual story. Try to make it a continuous line that, when you look through it yourself, is a pretty good read. For the rest, try to have fun. Writing is pretty much like drawing. Just write in a style that you think is pretty, and write whatever you want around the general idea that you have.