Board Thread:Questions and Answers/@comment-26009886-20150118153540/@comment-25891214-20150119061042

Like Tricoro said, it will appear once only (if you catch it at the first try) but if you didnt it will appear again and again until you catch it, the MBox can even appear again in the same ruin if you missed it the first time but it will be the same MBox that you missed (if it was brown a brown MBox will appear again) missing it intentionally hoping that a better MBox will appear its a waste of time because it will never happen.