Probably only minutes, though the tripping person might sense time differently and the ritual is not limited to one person at a time. At this point in the journey pilgrims would be exhausted by the long road in the dark tunnels and in this part of the path rest their bodies while they soulsearch.<br/><br/>Aleria can probably deduce with her arcana skill after a minute or so that any magical effect the pool would have other than starting the trance would come from and depend on the outcome of the ritual.