I'm not an asterioidean by any means, but from my experience, I would say that it is a harmless detrivore starfish. The shape of the crown and the coloration do not make it a threat, in my honest opinion. However, most starfish are better left in the ocean, since aquarists have yet to keep them long term successfully in home aquariums.
You may put it in your tank and it does well for years... or you may put it in your tank and it eats all your corals, basically. Sorry I couldn't give more information. Thank you for sharing the picture. Quite pretty.