I know that Xerneas and Yveltal are shiny locked, but I’m pretty sure that the Legendary Birds and Mewtwo are not.
One thing I want to ask is if the shiny Legendary Bird that you encounter can be soft-reseted at the Sea Spirit’s Den. I know that people have been soft-resetting for IVs and Natures outside the Sea Spirit’s Den, so I take it that you can soft-reset for shiny too right?
Please don’t tell me that they are shiny locked, because I’ve already checked and there are some people obtaining the Gen I legendaries for shiny, so my main question is can I still soft-reset for shiny outside the Sea Spirit Den, because I’ve already encountered it and saved the game, so I want to know if I can still get it shiny.
Also, when you comment please tell me the source where you obtain the information from, if you have gotten one yourself, please tell me if you encountered it shiny the first time and it stayed shiny.
I saw a comment on one of Marriland’s videos that they found a shiny Moltres. Based on the answers given, I believe that the birds can only be shiny if they’re shiny on the first encounter. So, no, you can’t soft-reset at the Sea Spirit’s Den. For MEwtwo, I do believe you can soft-reset.