A cheese tactic for beating legendary animals
So when you step out of the fighting arena it takes some time to reset the combat. Shadow of Nyx becomes available as soon as the enemy loses sight of you, even for a moment. The main point is tamed animals' combat reset time is slightly longer than the player's. If you manage to enter the combat arena during this very brief period using Shadow of Nyx, the beast is technically unaware of your presence so it won't attack your pet. You just stay invisible inside the combat arena till your pet exhausts full HP of the legendary animal.