I think that not many people use fountain pens these days.
I have been looking for a few nice, deep purple inks with a drop of blood-like colour.
In fact purple used to be a sign of wealth or power. It was used by kings, for example in Byzantine Empire.
They used to extract purple dye out of some sort of sea snails. The numbers could go in thousands.
"Twelve thousand snails of Murex brandaris yield no more than 1.4 g of pure dye, enough to colour only the trim of a single garment."
There is also one nice ink I like to use (and it's cheap): Rohrer & Klingner Scabiosa.
However, as you can see, it isn't that much deep. Im wondering if anyone came across something more like a mix of these 2. The dark purple one is scabiosa, and the second one is diamine oxblood. 