Flail Head Acid is needed to create the Flail of Ages +3. Howver, with only one or two heads, you can forge an incomplete version of the Flail of Ages. This head adds acid damage to the flail, which is handy to kill trolls. This item appears in Baldur's Gate II: Shadows of Amn. Glacias drops it when he is killed.
|“||This is one of three flail heads belonging to Lord Arnise. Not all three heads are required to assemble the flail.||”|