Viper's Lash (3.5e Martial Artist Maneuver)
From D&D Wiki
Your limbs lengthen like a cobra stretching to attack
Level: Tempered 1
Prerequisite: Dex 16
Description: Increase the area you threaten by 5 feet while the stance lasts. For instance, if you normally threaten a 5-foot-radius area (normal for a Medium creature), you now threaten a 10-foot-radius area; your space/reach is now 5 ft./10 ft.
Special: If you move more than 5 feet while this stance is active, the stance is automatically dropped.