This aura shows the cooldown of your Sepulcher's Savior shield, with text indicating its current status.
By default, this shows the mode you are currently in; using your shield will switch from this mode to the opposite.
If you want it to show what which mode you'll be in after pressing the button, check "Inverted" in the Custom Options tab.
If you are using a non-English client, you will need to change the text used to detect your shield's status in the Custom Options tab.
If you want to use Conditions to make cosmetic changes, you can reference the Name value from Trigger 2, which will be "Offensive" in Offensive mode and "Defensive" in Defensive mode.