Indeed, naginata are a staff with a bladed end - not always bo, i have a 4 foot (jo) with 2 foot long blade in the style of the edo period (they tended to be shorter and generally only wielded by women at that time - they were often used as the last line of defence of a home, the women with their naginata).
http://www.naginata.org/naginata.html
I would love to learn to wield one, but there are only 3 schools in the entire UK, and no governing body. Oddly it's rather big in France, but the French authorities frown on the British travelling to France to learn
In Vanguard terms I would be surprised if they are not available in Kojan. I am planning on finding out which weapon skill they use (I suspect polearm) and learning it alongside a more traditional tanking weapon skill so that when I travel to Kojan I can pick one up
Small wonder my favourite weapon in EQ1 was my War Marshall's Bladed Staff
