Enchanted creature can't attack, block, or transform.
Sacrifice another permanent: Attach Bound by Moonsilver to target creature. Activate this ability only any time you could cast a sorcery and only once each turn.
4/8/2016 Activated and triggered abilities of the enchanted creature that would cause it to transform can still be activated or triggered. If those abilities have any other effects, those effects will happen.
4/8/2016 You control Bound by Moonsilver even while it enchants an opponent’s creature. Only you can activate its last ability.