Flanking Maneuver

Epic Tier
Prerequisite: 21st level, Dex 17, trained in Acrobatics
Benefit: You can move diagonally even if a wall corner normally blocks such movement.
    You can move through enemies’ spaces. You provoke opportunity attacks for this movement as normal. You can’t end your move in an enemy’s space.

Published in Player's Handbook, page(s) 207.