A narrow crevice in the rocky foothills of the mountains continually exudes foul, sulfurous gases from deep within the earth. About thirty paces inside the crevice, brimstone containing Ignem vis collects on the walls. The crevice is so narrow that even a small person can only negotiate it with difficulty, and the fumes and heat are so potent that an unprotected person will die within minutes. A simple Perdo Ignem spell can protect against the heat, but the gases are a different matter. Creo Auram will provide breathable air, but even so it would be difficult and dangerous to collect the vis. The fumes are also highly flammable, and those who attempt to penetrate the crevice using any kind of open flame as a light source will be in for an unpleasant surprise.
Breathed in small quantities, the fumes from the vent might induce visions of the past, or even of the future. Their deadly virtue might be collected in some manner by a crafty Magus for use in the creation of poisons. The superstitious mundanes who live nearby regard the crevice as a gateway to Hell, and will be deeply suspicious of those who dither in the vicinity.