Flail Head Fire is needed to create the Flail of Ages +3. but with one or two heads, you can forge an incomplete version of the Flail of Ages too. This head adds fire damage to the flails, which is handy to kill trolls. This item appears in Baldur's Gate II: Shadows of Amn.
It can be found in the room with the golems, statue in the middle of the room in the De'Arnise Keep. If you only pick the flail head, you can avoid a fight.
|“||This is one of three flail heads belonging to Lord Arnise. Not all three heads are required to assemble the flail.||”|