Magical powers were once thought to 'be attached to' the stone. [=the stone was once thought to have magical powers]
Little credibility 'was attached to' his story. [=people did not think that his story was very credible]
The shy child 'attached' herself 'to' her mother [=stayed close to her mother] during the whole party.
(..) He will need the strength and brilliance of your mind. You must forgive him, as he must forgive you. There's no need to remain attached to a dying animal like me. What if I don't want to? Then I shall have to command you, being your King. My lady. (..)2017 TvShow: Vikings Title: On the Eve Season: 4 Episode 19