Sea Mountains

While there are only a few of them, these massive mountains, rather than being tall, cover a wide area. Most people seek them out for the various hot springs at the top of them, however they house multiple monsters and the widely sougth after Pyre Gems. Underneath these moutains is a vast network of magma caves, which is what heats the hot springs at their top. This is also where one would find most of the monsters that live in the area. It's said that no one has ever fully mapped out/explored the inside of the caverns yet.

Geography

The overall journey up one of these mountains is relatively not difficult. Very few areas have steep clifs and sharp inclines. Most of the area has an upwards incline that goes on for a kilometer or two until you reach the top. Jagged rocks litter the place and sometimes one might find a Barsm or two, but otherwise it's a fairly easy trip to climb over/make.
There are natural entrances into the mountains themselves that go down into a series of connected magma caverns. The inside gets hot very quickly, and most people can only stay/endure the heat for a few hours before they need to head back out. Magma flows fairly steadily inside these mountains, often right next to some of the paths that one can travel on.

Type

Mountain / Hill