Sacred 2:Noble Elements
This is in a cave north of the little hamlet of Bluestonbury. If a player crosses the bridge and keeps to the north side of the hill, they can follow a trail which will take them up to a camp where Kobolds are fighting elves. There is a little stream to be crossed, head North East to a cave that has several statues surrounding a fountain of T-energy.
All of the inert/noble gases as Guardians:
Guardsman of the Wardens Helium
First Guardian of T-Energy Argon
Second Guard of T-Energy Neon
Third Guardian of T-Energy Xenon
Fourth Guard of T-Energy Krypton
Guardsman of the Wardens Radon
The device in the center appears to be a miniature of the Great Machine's central collection reservoir found at the climax of the game. Unlike the one found on Seraphim Island, this one seems to still be complete and fully functional.
It would appear that the layout of the cave as it appears in the picture above, is a representation of the final battle of the game. And if it actually is a representation, the nameless guardians aren't quite so...nameless.
Mer-kil, the dragon you need to consult as part of the main quest, will tell you that the hub for the Great Machine is in the Jungle area, in the center of the lost city. He will also tell you that the city used to be an outpost of the High Elves back in the day, before the city became evacuated, lost, forgotten and abandoned.
This cave was likely built by High Elves sometime AFTER city was abandoned and the Temple Guardians moved the Great Machine to the wastelands during the Great War. The description of the machine, the fact there were 4 guardians and such could have been passed down verbally along with the gizmo in the center - possibly the device was brought along by an evacuee of the ancient city. For all we know, the ancients could have been making miniature versions of the Great Machine as souveniers or it could be a prototype.
Word of mouth instruction can become easily altered and no longer anywhere close to the original. For instance, if you tell someone that Bobby has a blue ball - and to pass it on to the next person in the queue of say, 100 people, by the time you get to the last person, you might hear something about how Bobby is a frustrated pervert who needs a blue pill. It all depends on how well information is duplicated from person to person and how well that information is passed onto the next.
Given the level of chaos during/following the Great War, it's easy to see how information and technology could have been lost. The word "guardian" may have ceased meaning anything other than "a humanoid in armor standing guard" by the time the cave was built. Why should it? The Temple Guardians weren't around any more. Except for the one that was entombed in the ruined temple (where the Temple Guardian starts his game), they were all busy guarding the Great Machine or destroyed in the Great War. No one knew or saw anything remotely like the Nameless Guardians in ages. A humanoid guardian would have been something the High Elves would have had experience with.
The fifth and sixth guardians - Helium and Radon - may represent the Temple Guardian corps who are the first line of defense for the Great Machine.
This is only a theory... Until someone comes up with evidence to the contrary or confirmation from the developers, that's pretty much all it is - a theory. Please take it with a grain of salt...