Steam vents and geysers of the Broken Lands
by RobinCanon mentioned and fanon (amongst myself) added are steam vents and Geysers in the Broken lands
Steam vents (Ziik Vel" (Wet Skin)
These are nothing more than tunnels(often minor in size, yet passable is possible too) where steam passes through to the surface, enters the air and either rises up contributing to the weather/moisture ecological systems, or cools and clings to nearby surfaces (hence the caves are called "Ziik Vel" (Wet Skin) in Gobbleton (and similar in the other humanoid tongues.) Normal steam vents are 100-140 degrees Celsius, and cause 1d4 damage each round to exposed organic matter. (Many humanoids use this as a way of food preparation in a bowl on a large stick this is called "Pen Heras (Pan Cooked)", (or just stick it on the stick called "---sort food---SjashLick")
Geysers (Sprtin Gehert Idar=Spring spitting Hot)
Groundwater percolates through porous rock into fractures deep underground, where heat from a nearby magma chamber superheats the pressurized water to a temperature above the boiling point of water at surface pressure. In hot springs the rising superheated water is cooled below the boiling point by groundwater before reaching the surface. In geysers the superheated water collects in underground pockets. There a small drop in pressure caused by the release of water at the surface flashes the superheated water into steam, which expands and ejects a column of steam and water into the air. When the supply of steam and hot water is exhausted, the spouting stops and the cycle begins again.
Hot springs (Spritin Idar) are not that hot to become steam, and just rise up.
There is a third variation of Mystara Geysers and Steam vents; this is the High Steam vent. The common steam vent version is heated water IN the rock somewhere above the Magma. On Mystara in the Lower Broken lands there are several locations where large amounts of water hits the flowing-by Magma (this magma passes by, and though cooled significantly, it remelts a few moments later due nearby still flowing magma), and is explosively (canon) transformed into steam with a loud noise. The steam rapdly rises, and most of it becomes part of the lower Broken Lands Ecosystem when cooling down turning into "Zilk Ceyos"(Wet Rocky Terrain), some of this stram passs through steam vents.
High Steam vents are so hot that within a a 100 yards organic matter takes damages due the heat, and even rocks eventually shatter. Metals rust within a Turn. This damage is so high that a saving Throw or protection from Heat is required each round to prevent 1d4 damage each round in the area. For each turn/10 minutes in the area all metal loses 5% of its mass due rust. Multiply the current magical charge by 2, this is the extra eroding time is needed to remove one magical charge in this effect before rusting takes place. A +5 Sword thus requires 5x2=10 extra Turns before losing one charge of magic becoming a +4 sword, etc etc. Magical weapons are thus signigficantly more resistant
Rustmonster often come to hunt for this easily accessible rust, yet even they cant stay long. They can resist the first 10 minutes/1 Turn of heat damage though. Creatures fully Immune to heat (or fire) are not affected
Within 10 yards of the vent damages are doubled, and no protection from heat prevents a minimum of 1 damage each round. A protection from Fire does.
For the unlucky coming incontact with this superheated steam, flesh is literally riped from the bones for 4d8 damage each round. and that body part is lost unless regeneration is active. Protection fom Heat will NOT prevent this damage which is a combination of heat, and pressure on impact.
Magic on items is flushed away with 1 charge each round!!!, yet will function as long as some magic resides.