I recently came across this:
August 3, 2009 in Personal Files by Simon Coal
Files and Records, begin taking dictation, please.
The Festival of Carapaces was amazing. All those little effigies burning in the night sky! It’s a great experience, to put all your regrets and triumphs into a woven-grass spider and then light it up. It’s very… rejuvunating. And the food! Dishes I haven’t had since I left home for the academy, drinks and dancing and music. I feel like a new man. It wasn’t quite like home, nothing is quite like home, but it was enough.
There is also a reference to it coming up made in an entry in Simon's log on July 19, 2009. However, there is no mention of it in posts from similar time periods this year. This could be because the festival is tied to the Intaki Calendar, meaning it would be almost two years between intervals on the Eve Standard calendar.
I bring it up here, it hopes that Simon (or others) might flesh this holiday out a little more.