Invigorating Bash is a star within the Constellation The Steed in Elder Scrolls Online.
This was added in Update 6 with the Champion System. It gives you a 20% chance to restore 437 Health when you Bash an enemy (at VR14). 10 points in the Steed Constellation are required to unlock it. Once unlocked the player will acquire this bonus automatically and across all characters on their account.