Explain Javelins to me?

Someone gifted me a Buriza-Do Kyanon, so I’ve been testing it out. My merc has insight and I barely have mana issues now with this weapon because it does more damage and fires slower.

Not sure if I’m in love with it or not but I noticed quickly that my mana bar stayed full except for boss fights or tough mobs

It works for now. Probably better in a physical build tho I would assume