Sentinel.

While Finarfin is defending, he gains:"Response: Cancel a shadow effect just triggered. Then, cancel all damage dealt to the attacking enemy until the end of the round. (Limit once per round.)"

But Finarfin spoke softly, as was his wont, and sought to calm the Noldor, persuading them to pause and ponder ere deeds were done that could not be undone...
–The Silmarillion