I like how it is made from some magic elemental stone, but as mentioned, some real details on how it benefits the wielder would be go. It has great presentation value, but what justifies the effort in creating it? Perhaps it works exceptionally well against earth-aspected opponents? As a focus for earth magic used by the wielder?
This is another nifty little detail. One could easily have any _naturally_ occurring holey stone have some power over the supernatural in your world, especially given how powerful these types of beings can be compared to a common person. The same way silver is bane to werewolves, and running water is to vampires, a holey stone helps peel back the veil spirits and their like use to hide from humans.
An interesting idea - it can be made non game specific simply by indicating that the drinkers will be affected by magical rage and leave it at that. Timing, how to resist, etc, can be implemented by whoever uses it.
What this post really needs to improve it is _why_ the lake causes rage? Is there an imprisoned evil god buried in the sediment below the waters? Did 100 berserk demons die in a battle eons ago on the site? Etc. Go to Comment
Certainly a great take of the Dancing Sword idea. This could easily be made rare and not cookie cutter by the need of specific knowledge, as well as for the sacrificing person needing to be exceptionally skilled.