Golems are magically animated postmortal creatures. They are physically invulnerable and ageless. All known golems speak Glyph and can teleport, but those may be learned abilities rather than innate powers - Monica can do both but is not a golem.
Mayahuel may be the only person still alive who knows how to make golems and she's in no hurry to do so. The process is very unpleasant: at least one human or other creature is burned alive, and the ashes mixed with the clay that forms the golem. There is no known way to destroy or even harm a golem by physical force, but a sophisticated Glyph reader with the right access can manipulate or alter the programming that animates them.
Tepoz is the oldest known golem, and is believed to be a prototype or test unit. He is the only golem with no memory of a previous life, and also the only one whose current appearance doesn't echo their previous body.
Mayahuel taught the art of golem making to some Lanthian priests for reasons of her own; she got a reasonable approximation of immortality by having them turn her into a golem, at the price of being turned into a golem.Afterward, when Mayahuel was unavailable, the Lanthian priests made another golem (or three, depending on how you want to count). Brandi, Bud, and Jin were killed and made into the Chimera; whether their plan would have worked with better planning is academic. They're not known to have tried any previous golems before their big project - and of course afterwards they were dead. Later the Chimera was split, allowing the girls to exist independently again.