A Fury Orb is a type of item. When a runemaster attaches a Fury Orb to a character, it becomes a Fury Rune, which makes the user in berserk state.
Suikoden II[]
L'Renouille (chest).
Suikoden III[]
Found on a corpse at Mt. Hei-Tou.
Suikoden IV[]
Defeat all five levels of training with Reinhold and you will get the Fury Orb.
Suikoden V[]
Can be bought in the headquarter Rune Shop, and various rune shops.