Spectral panther

Spectral panthers were supernatural panthers touched by the energies of the Shadowfell who were fond of hunting humanoid prey.

Description
Spectral panthers were massive cats, often between 10 and 12 feet (3.0 and 3.6 meters) in length. They moved back and forth between corporeal and incorporeal forms. In corporeal form, their eyes were pure black, reflecting no light whatsoever, and their fur shimmered with illusions that made them still appear insubstantial and translucent. This made them very good at hiding and moving stealthily, especially when concealed in shadow. They possessed sharp claws, and some had a spike at the ends of their tails.

Abilities
With some limitations, spectral panthers could fade in and out of being completely incorporeal. Some could freely make themselves insubstantial before also becoming completely invisible, while others could only manage this feat a few times per day for relatively short stints. When in their corporeal form, spectral panthers could still interact with or attack incorporeal creatures, and likewise while incorporeal, they could strike at corporeal prey. Owing to having been touched by the magic of the Shadowfell, they could move between the Material Plane and Shadowfell during dawn and dusk.

The beasts radiated an aura of fear, and just being near one could leave an adventurer shaken.

Behavior
Spectral panthers fed on both the flesh and the fear of their prey. As such, they preferred to hunt intelligent prey, especially humanoids, because their fear was more satisfying. Spectral panthers were themselves highly intelligent, and would toy with their quarry, stalking it for hours in order to savor its fear before finally pouncing.

Combat
Spectral panthers preferred to ambush their prey. They would emerge suddenly from their invisible, spectral forms to strike quickly before retreating and vanishing once more, only to return for another surprise strike.

History
Both shadar-kai and dark creeper hunting parties were known to use spectral panthers as trackers and killers.

Spectral panthers were unheard of in Faerûn until sometime in the 14 century DR. They gained notoriety in the late 1360s and early 1370s DR when they were identified as being responsible for a number of savage killings across the continent, ranging from Hlondeth to Waterdeep. The only common thread between the victims was that they had been wizards who practiced shadow magic, but it remained unclear at the time whether the beasts had been drawn to the wizards’ magic, had been summoned by it, or if instead the creatures had been intentionally sent after these spellcasters.