It's a new Halloween illustration this time. Yeah Yue! (please comment if you have the full illustration). The game will continue until December of this year. More info here.
Also, CLAMP will be illustration Nakamura Aki's debut detective novel, ロジック・ロック・フェスティバル 〜Logic Lock Festival〜 探偵殺しのパラドックス. It will be released November 14th. More info here