The prereq for the Feat is lowered to 14 DEX. (You must have the appropriate overrides in place to take advantage of this, see the downloads topic)
Whenever a Improved Whirlwind Attack is preformed, you character will preform his Whirlwind attack as usual.
However, there is an extra Damage applied to all hostiles within the same range as your Whirlwind attack reaches.
The Damage Calculation is:
Character Levels/2 + 2d6
If the User is an Epic Fighter (21 Levels), this damage is doubled.
The Damage type is:
The Damage Power is:
Plus Three. (Used in damage reduction)
NB: This extra damage is not subject to AB vs AC checks, Concealment or Critical Hits. It will also ignore other defensive capabilities, such as Stealth and Epic Dodge and so on.