Actually, there is something you can do! Do you have any of that man's possessions? I won't be able to summon him as long as he remains in the manor, but I could summon him if he were to leave it.

[ This plan will 100% not work, thanks nameless skeleton arriving in the carnival in the dead of night. A for effort, tho ]

The other skeleton was the one who fought Lambert in the ballroom. The Prince might trust him enough to let him out of his sight for a moment or so.