Or they could have stuck the silence spell on one of themselves, and that person just stand next to the sarcophagus - I assume if the sound of the incantation doesn't reach the target, it won't work. (Not 100%, sure, but certainly easier to try than flying after someone who is a natural flyer.) Or, stick it on an arrow/bolt and use what you can to make sure you hit Oban... again, not perfect. I think the first one is better, as it would make him come to them. But ultimately, as I said up thread, they are seriously feeling the effects of not having any ranged combatants. Heck, why don't the few semi-fighter types and the one fighter type have secondary ranged weapons? Come on. I know its D&D, but you cannot expect to use your bestest attack every round. Have back ups and attacks to cover other types of attacks.