There are several things.
First, a Dwarf usually (and this is the norm, not the exception) becomes a Geode by losing his twin brother. Aventurian Dwarves are usually Twins, or even triplets.
Losing a twin has two results :
a) he left-over brother seeking a way to free the spirit of the "lost brother", and this often or usually becomes a life-long task for them
B) they become able to use magic, though I don't remember anmore, how.
And Geodes are the ones from which the aventurian Druids came from, because the very first Druids were actually humans learning from Geodes.
The second thing is the origin of the Temple : During the ages of the saurians of any kind, long, long, long before any human went deeper into Aventuria, the saurian races built up a temple for a Goddess called Charyb'Yzz.
Her modern name is Charyptoroth (always remember that this is German pronounciacian, as far as I know !), and she is nowdays the demonic counterpart to Efferd. Every one of the Twelvegods has such an demonic counterpart.
Now, Charyptoroth's fate is kind of unsolved, but there are rumors that she might have been indeed a Goddess of water, decided to go into the demon realms for battle - and got ost there. So, she slowly transformed into a demon herself.
Even in background lore, this is unresolved ... There might still be some "godly essence" in her, but all in all she is regarded as a demon nowadays - and as he demonic counterpart of Efferd.
And this is the reason why so many foul-minded creatures are there under the temple.
The temple for Charyptoroth was kind of "shielded" by consecrating the upper part as/for a proper Efferd-Temple, but its deepest core is still connected with Charyptoroth.
Once, I wrote into the official TDE forums a plea to get this Goddess back again ( = out from the demonic realms), but even as a proper Goddess again, she would be tainted with demonic influence.