A flanged mace is the common counter to chainmail, circa 13th-century European armored combat. A curved sword is better for unarmored or those in animal hide like leather.

A mace (general) is a club with a head, which packs a more diffuse wallop than a bladed weapon or a spiked weapon. Spikes on a mace (such as a morning star) can help to focus and to punch through armor.

Not to be confused with a spiked flail, in which there's a chain between the handle and the head (a spiked ball or flanged star, like the one held by the Witch-king of Agmar) The chain helps circumvent shields, but it becomes very easy for the flailman to hit himself. Kinda like nunchaku.

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