The Wild Hunt exists in all the lands where Druids and their deities dwell. It is a physical manifestation of "life force" with aspects that change depending on the region it is manifested in. In the vast plains of the Rovers of the Barrens, the Master of the Hunt is known as Kernos. He appears as a warrior wearing a bison helm and carrying a warclub. Kernos is accompanied by a pack of savage ebon black hounds.
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The Hunt appears whenever there is evil in the land (as in the case of an
evil temple or an evil priest of the 12th level or greater coming into the
area, or what the DM decides is a grossly evil act)

When the Hunt passes, the noise of the howling dogs or the Hunt Master's horn can be heard for miles in the night. If this noise is actively pursued by any being, they will become part of the Hunt when they sight the pack and its master! If the Hunt passes by any given being. In that case, they must make a magic saving throw, or a WIS saving throw with a DC of 20 if they look at it (Those attempting to avoid looking at it have a 25% chance of resisting the urge) or join the Hunt. When any given being becomes part of the Hunt they take on one of two roles: they will be the hunters or the hunted! If the being joining the hunt is connected to the evil that summoned the Hunt, they will become the hunted. If the being opposes the evil that summoned the Hunt they will become hunters, and if the being was indefferent to the evil that summoned the Hunt there is a 50% chance they will become the hunted, or the hunter.

The Hunt always begins ten miles from the source of evil that "summons"
it, and for each mile nearer the source of evil when the Hunt is spotted, and they are indifferent to the evil that summoned the Hunt, the chance of their become hunted instead of hunter increases by 10%. The Hunt will always pass close by the source of evil that has created it (never going into a building, but going within inches of the building and passing by). After passing by, it will travel on in a random direction for ten more miles.

There will only be one Hunt on the Prime Material Plane on any given
night, and it will always be drawn to the greatest evil in the area
(decided upon by the referee). If the Hunt finds a being to hunt before
finding the source of evil, it will attack that being to kill it, and then disappear as it reaches its summoning source. If the Hunt does not find a victim before it reaches the source, it will travel on for another ten miles and every being that sees it and does not make their saving throw vs. magic will have a 90% chance of becoming the hunted!

If after ten miles, no being becomes the hunted, the entire pack will turn
on the nearest big game creature around (deer, stag, bear or anything
partially dangerous and non-intelligent). All during this hunt, the beings
that have come along with the Hunt must travel with the Master, and they
must attack whatever becomes the hunted. All beings that have been taken in as hunters will attack the quarry (whatever it may be) and if they do not succeed in killing the being, the Master and his hounds will take over (but only when all other hunters have been incapacitated) and they will either kill or be killed.

The magic of the Hunt will catch up and sweep along any who become
part of it, so that, whether mounted or on foot, they will be able to keep up with the fast pace that the hounds set.

The Hunt generally pursues on the ground, but it has the ability to run right into the air to fly over obstacles or especially difficult terrain.

When the hunted being has been run down, there is an instant melee to
the death. All participants must fight on to the death to the best of their
abilities (no holding back).

The only ways to prevent being killed as the object of the Hunt are to run
out of the 10 mile radius of the source of evil, to elude the pack until morning, or to slay the Master and his pack.

All beings that have been in any part of the Hunt have a 50% chance of becoming ensnared again with every sighting of the Master and his pack (no saving throw).

There have been legends of epic battles between the Master and his
hounds and some of the greater heroes of the past. In these legends, the
Master and his pack have been slain, only to disappear in the darkness
and appear somewhere else the next night, proving that the force that
creates the Hunt is eternal.

​Kernos, the Master has glowing green eyes and is shrouded in shadows. His head is crowned by a great bison helm, and he wears a suit of black leather. The Master never speaks.

He runs a few feet behind his pack of hounds and will sound his horn at
every 1 mile increment in his chase. He uses a +3 war club in battle.

These huge black hounds have licks of green fire for tongues and green fire for eyes. These flames do no damage but they make the whole Hunt cast an eerie green glow. The beasts will never attack the hunted until all the beings that have drawn themselves into the Hunt have had their chance to kill. If the pack is killed, the Master will then battle the being. The death of any member of the pack goes unnoticed by the rest and it disappears after the battle is over. The hounds attack as 8 hit dice monsters for AD&D.

Thanks to the amazing Matthew Fenn for compiling and editing together my blog posts on the Bone march into this amazing companion. Get your free copy here. 1drv.ms/b/s!AhghegQBK0OJjh0kidPPFvl903ao