2021-03-19 : If Bound in Silence becomes attached to a creature that’s already attacking or blocking, the creature continues to attack or block as normal.

2021-03-19 : 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.

2021-03-19 : Tribal is a card type (like creature or instant), not a supertype (like legendary). The type carries no rules that affect how it’s cast or how it behaves on the battlefield; it just allows the card to have creature types without being a creature.