Underfoot (BotB) (Combat)Source Blood of the Beast pg. 23
You clamber in and around your enemies’ personal space to devastating effect.
Prerequisites: Dodge, swarming racial trait.
Benefit: You are able to share a space with a hostile creature at least one size category larger than you. You gain a +2 shield bonus to your AC while occupying an opponent’s space, as well as a +2 bonus on all attack rolls against the creature whose space you share. Creatures you share a square with take a –2 penalty on all concentration checks. Entering a space occupied by an opponent provokes an attack of opportunity. This ability does not stack with similar abilities providing a creature benefits for being in another creature’s space, such as a mouserACG swashbuckler’s underfoot attack deed.
Special: This feat counts as the Disruptive feat for the purpose of qualifying for other feats that have Disruptive as a prerequisite.