Mystery Eldritch Invocation search

New Eldritch Invocation cropped up in a campaign with a ton of shared source books in dnd beyond. Its called ‘Hunter’s Grimoire’ is from some source book and we searched dang near all of them and haven’t found where its from. This is a 5th level dnd 5e 2014 warlock please help is we’ve search for 4 hours and have found nothing.