From the BGTSCC Wiki: You limit yourself to two attacks per round but your AB is raised by two for every lost attack. You additionally gain a tumble skill bonus of twice the amount of attacks lost, and a dexterity bonus for every attack lost, owing to your increased attention on positioning. Additionally you do two points of extra damage when you hit.
Use:
You drag the feat onto your hotbar, so it can work with modes like flurry. However, Sembian Fencing, Athkathlan Triparite and Northlander Hewing are mutually exclusive.
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This is based purely on BAB. With 26 BAB, you would keep your 2 highest attacks and lose your 4 lowest to gain a +8 AB. WIth Greater Flurry, this all stays the same. You gain +8 AB to your 2 hightest attacks PLUS the extra flurry attacks. I expect fighting with 2 weapons would work the same way.
Notes:
DEX AB & EB from items do not stack with Sembian Fencing.
The in-game description incorrectly states it buffs BAB.
Sembian buffs are bugged from 11 BAB to 15 BAB (3 attacks). Instead of +1 DEX and +2 AB/Tumble, it gives +5 DEX and +10 AB/Tumble.
My experience with Unarmed Strike differs from quality control's feedback in the forums. While the Character Screen displayed the increase to AB like equipped weapons, closer examination of the combat log showed Unarmed Strike's AB unchanged.
