So what uses did you find out for this item? The cluebook mentions only that's it's a mysterious artifact, and give out one of its uses. I've got 2 so far, one good and one bad.

_Eradicates player holding it when using Quatloo coins in slithercult dungeon.
_Artifacts at (8,8) in E2.

Is there any more to it?

I suggest that you only use it to get the powerful treasure from a hut near Swamptown. Using it at other times may prove detrimental - the one you mention also if you drink from a luck fountain in the desert while holding Fizbin, everybody dies. I did not mess with it to find out what other dire effects may arise but I would be careful.

I always sold them at the nearest opportunity.

Never thought there might be some use.

The hut near Swamp Town, is that the one which collapses after touching something?

It is a hut to the NW of Swamp Town and you must hold the Ancient Fizbin to enter it and collect your reward.

Sorry but what exactly is the luck fountain in the desert? Is it the desert in E4 and F4? I tried the wells there (except for rememberance; not enough money yet) with Fizbin in pack but no one died. Tried the luck fountain in Baywatch, but no one died either.

if you drink from a luck fountain in the desert while holding Fizbin

I would really have to try again as I do not remember - its been a while but the emphasis is on holding it - having it in your pack isn't the issue.

What do you mean by holding? I can't equip it, so having it in my backpack is the best I can do.
For the quatloo coins machinces and the house in the swamps having it in one's backpack was enough for it to work

Crap, I head from a YouTube to get rid of it! Now I find I need it!