text: If you put Bound in Silence onto the battlefield without casting it, perhaps using the "recruiting" ability of a card like Amrou Scout, it will enter attached to a creature. You choose that creature as you're putting the Aura onto the battlefield. This doesn't target that creature, so you could have it enter the battlefield attached to a creature an opponent controls with hexproof, for example. If there's no creature on the battlefield it can be attached to, it stays in whatever zone it was in.