Corrupted Hydra, The Horror of Yolst

The Horror of Yolst is a legendary corrupted hydra that resides in a large swamp-like mire that has been tainted by the Abyss. A forgotten temple to the demon Prince Orcus curses this mire. This temple used to house a portal to the Abyssal plane over a thousand years ago until it was mostly destroyed by flooding and was forgotten. The residual magic around the place where the abyssal portal once stood has caused this apex creature to become corrupted along with the land, causing the dead to rise. The Horror of Yolst was the apex creature within this mire, and it made the ruins of this forgotten temple its lair. What once was a normal hydra, became tainted by the remnants of the abyssal portal that once stood in these ruins and became an abomination. Five heads atop long spindly necks make up a majority of the creature’s mass, with large growths along its torso that resemble shattered bits of turtle shell. Tough dark green scales cover the outer portion of this creature, and flesh-colored scales lining the underbelly, with a slug-like skin beneath the scales. This skin can ooze a thick mucus that causes the water around the hydra to become sludgy and hard to walk or swim through. The central head resembles that of a large snapping turtle but with a protruding larger jaw and sits upon a shorter neck. From this central head, the hydra can expel its steam breath attack. The four other heads have long matted fur-like hair with teeth that have grown too long for their maw. Although its heads can be severed, the hydra magically regrows them in short order. The tail of the beast is long and spindly, with poisoned barbs that it produces from the end.

Hydras normally dwell in swamps far from civilization. The corrupted hydra's lair is a dismal ruin that is at least partially flooded, providing pools where the hydra rests. The lair is littered with the bones of previous victims and the fly-ridden carcasses of fresh kills. Other natural creatures that make the swamplands their home tend to avoid the lair of the corrupted hydra, for fear of being part of its next meal. The stench of death and decay or a portal to the Abyss is not out of place in the lair of a corrupted hydra.

Lair Actions

On initiative count 20 (losing initiative ties), the hydra takes a lair action to cause one of the following effects; the hydra can’t use the same effect two rounds in a row:

• Pools of water that the hydra is in become corrupted. Mucus is expelled from the hydra creating difficult terrain for 20-foot-radius.
• Any pool of water the hydra can see within 120 feet of it surge outward in a grasping tide. Any creature on the ground within 20 feet of such a pool must succeed on a DC 15 Strength saving throw or be pulled up to 20 feet into the water and knocked prone.
• A cloud of noxious mist fills a 20-foot-radius sphere centered on a point the hydra chooses within 120 feet of it. The cloud spreads around corners and remains until the hydra dismisses it as an action, uses this lair action again, or dies. The cloud is lightly obscured. Any creature in the cloud when it appears or starts their turn in the cloud must make on a DC 15 Constitution saving throw, taking 10 (3d6) poison damage on a failed save and becomes poisoned for one round, or half as much damage on a successful one. A creature that ends its turn in the cloud takes 10 (3d6) poison damage.

Regional Effects

The region containing a legendary corrupted hydra's lair is warped by the hydra's presence, which creates one or more of the following effects:

• The land within 6 miles of the lair takes twice as long as normal to traverse, since the plants grow thick and twisted, and the swamps are thick with reeking mud.
• Water sources within 1 mile of the lair are supernaturally fouled. Enemies of the hydra that drink such water regurgitate it within minutes.
• Yellow tinted fog lightly obscures the land within 6 miles of the lair.

If the hydra dies, vegetation remains as it has grown, but other effects fade over 1d10 days.