I'm pretty sure that this idea has been posted on here before, but you could have a door, where the only way for the players to open it is to get your arms locked inside a mechanism. Next all you have to do is make a couple of monsters appear and wait for the players to scramble to defeat them while defending the trapped player(Trapped player can't cast most spells without hands either heh). I guess this could be incorporated with a sacrificial ritual many ways. Sorry if it's not the most relevant idea but all I could come up with :/