Weapon Group (Exotic Double Weapons)

(Unearthed Arcana, page 96, DnD 3.5)

[General]

You understand how to use the exotic double weapons associated with the weapon groups that you have mastered.

Benefit

Whenever you take a Weapon Group proficiency feat, you also gain proficiency in the exotic double weapons associated with that group. When you take this feat, you gain proficiency in the exotic double weapons associated with the weapon groups that you already know how to use. Some exotic double weapons require you to be proficient with two weapon groups to gain proficiency in their use from this feat.
Axes: orc double axe, dwarven urgrosh (must also have "Weapon Group [spears and lances]":feats/unearthed-arcana--90/weapon-group-spears-and-lances--3122/).
Flails and Chains: dire flail, gyrspike[^A] (must also have "Weapon Group [heavy blades]":feats/unearthed-arcana--90/weapon-group-heavy-blades--3115/).
Heavy Blades: double scimitar[^A], gyrspike[^A] (must also have "Weapon Group [flails and chains]":feats/unearthed-arcana--90/weapon-group-flails-and-chains--3114/), two-bladed sword.
Maces and Clubs: double mace[^A].
Picks and Hammers: double hammer[^W], gnome hooked hammer.
Spears and Lances: dwarven ur-grosh (must also have "Weapon Group [axes]":feats/unearthed-arcana--90/weapon-group-axes--3106/).

Special

If you include exotic double weapons from sources other than the _Player's Handbook_, the DM should assign those weapons to a weapon group as appropriate for the campaign. The lists above includes weapons featured in the _Arms and Equipment Guide_ (marked [^A^]) and _Complete Warrior_ (marked [^W^]).

Normal

When using a weapon with which you are not proficient, you take a --4 penalty on attack rolls.