Wellby succesfully cuts the thread. He thinks that it's disarmed.

OOC: as a head's up so you guys aren't waiting for it, this is a heavy stone and will probably require nearly every +1 you guys can contribute to a str check, whether that's through magic or having additional people help out. However you can't move it with the crowbar, you will have to grasp onto the stone to move it if you're helping, unless you can think of a more ingenious way of moving it.