Needs review
Source: Dungeonscape

Description: Dwarves have developed a variety of cunning tactics to defeat those foolish enough to enter their mountain redoubts.

Prerequisites: Base Attack Bonus +6, Knowledge (Dungeoneering) (2 ranks)

The Undermountain Tactics feat enables the use of certain tactical maneuvers, described below.

Stair King: To use this maneuver, you must gain the high ground bonus on your attacks against an opponent. If you hit your foe with two or more melee attacks during your turn, he must make a Balance check (DC 10 + your Str modifier) or be knocked prone. Your opponent can opt to succeed automatically on his Balance check. If he does so, he will lose his move action on his next turn, but he will Succeed automatically on Balance checks to resist this maneuver until the start of his next turn. Your opponent must make this choice before seeing the result of his Balance check. You can target a particular creature with this maneuver once per round.

Tunnel Fighter.- To use this maneuver, you must be the target of at least one melee attack from at least one foe while standing with walls adjacent to you on two or more sides. When you are attacked under such conditions, you gain a +2 bonus to Armor Class due to cover. (If you gain cover from another source, this benefit does not stack with it.) You also block line of sight for any spells or attacks made by your opponents, though your allies can fire through your space as normal.

Door Sentinel: To use this maneuver, you must fight defensively while adjacent to or standing in a doorway, a gate, or a similar opening in a wall. You must be adjacent to or standing in each square across the doorway's width. For 1 round after you fight defensively, you gain a +4 bonus on Strength or Dexterity checks to resist bull rush or trip attacks. Any creature attempting a Tumble check to avoid your attack of opportunity takes a -5 penalty on the check. Any creature attempting to tumble through your space takes a -10 penalty on its check.