Aquilonastra conande (often referred incorrectly as Asterina stars). These are the dark phenotype that are rumored to feast on zoas and other soft corals. They can proliferate quickly and spread across your tank. I'd remove if I were you
I agree, definitely a Asterina star. Some are good and some are bad. If you Google Asterina starfish you will get the same if not more results then if you typed in their "new name"