There is almost no information on the Mad Knight of Alken aside from the description of the Ring of Blades:
The Ring of Blades is modeled after the
mad knight of Alken's weapon of choice.
Increases physical attack.
The kingdoms of Alken and Venn
long ago flourished on these very grounds.
They were both founded by the same man,
but were reduced to rivalry and spite.
The image for the Ring of Blades is so small it is difficult to tell what kind of weapon it may be modeled after. It may be that it is many images of the same weapon repeated. If this was the case, the ring was most likely designed after a twinblade of some sort, which would make poetical sense considering the text that follows which concerns the joint origin of 2 kingdoms (just as the twinblades come from the same handle).
It is plausible that the Mad Knight of Alken was simply a knight in the order of the King of Alken who became famed for their so called madness. Or it may be that the Mad Knight of Alken founded both Alken and Venn, as there is no definite name ascribed to the founder of Alken and Venn in game.
We know that the kingdom of Alken once flourished in the area of what is now known as the Lost Bastille and we can therefore place the Mad Knights origins.