My ideas for Golems.
Creation:
A golem could be created by any dwarf mage (as is the correct term IIRC) using regents such as clay and gems, secret tomes, spell scrolls, laboratory text and notes. Spell scrolls could be discovered or invented by a Mage during a fel mood, which could then be used by future mages to produce golems, or they could be discovered through magical research and study. Laboratory text and notes could be jobs that mages do inside their laboratories, sometimes taking weeks, months or years to create, depending on the value sought. The higher quality the materials, the longer the golem will survive. The more laboratory work allocated to a specific golem, the more capable that golem will be.
Use:
A golem would work similar to a lever in that, when being created, you would determine exactly what the golem would do in it's lifetime. If, for example you want a golem to operate a water pump constantly without moving for the rest of it's life, your golem can be made in very little time, with fairly little laboratory work and made of cheap clay. Making a golem constantly haul buckets of magma from one site to another may be slightly* harder to create. Adding the ability to command the golem to stop pumping in an emergency requires more laboratory work to set up (but gives you more control over your creation), similar to a mechanic adding connections to a lever. The most competent golems would be capable of learning skills just like a normal dwarf, although being limited in what they were built for. A certain type of mood could cause a golem being constructed to become a Golem, thus achieving sentience and gaining a name and freewill.
*Understatement
Combat golems:
A golem designed specifically for combat would require much more work under this system then a simple hauler, unless used to guard a door and told to kill goblins who approach. A fully capable golem would require a mage or commander to instruct it on what to do at all times, thus requiring constant supervision to stop the thing from getting lost or confused. If the mage controlling the golem dies, the golem will continue it's last order at which point the golem does...nothing. Another mage can come over and 'reset' the golem like a weapon trap, thus allowing the golems to continue fighting after their 'master' dies.
Limitations:
Currently, all artificial creatures are absurdly powerful because of their design. They usually are made of very strong material, have no internal organs, do not bleed, have no fear, are immune to extreme heat and are MASSIVE. Sometimes so massive that it does not make sense for a clay cave-in to instantly kill it. Therefor a golem should be essentially a large, MAGICAL creature with all the weaknesses a magical creature should have. The more unlikely and unnatural a golem is (flesh before blood, blood before wood, wood before copper, copper before steel, steel before magma, etc), the more magic and preparations required to create it, and the more vulnerable it should be to banishment and other anti-magic stuff. Perhaps even having a "magic" blood layer of gems that can be hit to drain the golems magical energy, or even a magical 'organ' that can be pierced with heavy enough weapons. A golem should be near invulnerable to anything mundane, but should be at least killable by any civilization with any decent knowledge in magic. As the golem is completely run on magic, golems should have a lifespan equivalent to the effort, skill and resources put into the golem (but should not last forever, think 1050yrs for the exceptional ones).
Alternatives:
A 'golem' need not be dwarven in origin. An ancient such as in Warcraft III would also be considered a golem, although made of wood and sentient. A golem made from blood or toxins could also be made, which could run into a group of enemies and destroy itself. A golem made from organic materials could also be easier to construct, given that they are not that unnatural, and could get a bonus to abilities it would normally have (from it's material), such as the attributes of a tree if made from wood.