What's the Freakiest/Most Gruesome Things That You Have Put in your Campaign/World?

[Alzrius]

Pishtaco? Pishtaco - Wikipedia

A fish taco?

 

[Umbran]

Pishtaco? Pishtaco - Wikipedia

No. Less sentient. Basically, Star Trek "salt vampire" but with your body fat.

 

[Imaculata]

I have a vermin goddess in my campaign, who is also nicknamed The Lady of the Flesh. In a nutshell, she embodies grotesque mutilation. Much like a cockroach, she is almost impossible to get rid off, because she spreads facets of herself across worlds. These facets must exist inside a willing host (often female as is the will of the goddess), whereupon they become minor avatars of the goddess, called vessels. Her most dedicated followers are a tribe of vicious cannibals, whose leader is one of these vessels. She is gifted with the powers of a god-avatar, as all vessels are. The goddess can make clones of any body she inhabits, through a cocoon which grows an exact copy over the course of several days. Vessels are changed in body and mind, but retain any powers they already had before becoming a body for the goddess.

And so I had the goddess take hold of a former lover of one of the pc's and they were forced to fight and kill her. This lover had innate magical abilities that the goddess found very useful, so she also made a clone of it as back up.

 

[Blackrat]

I’ve managed to put dread into my player’s with some very simple tricks. They were exploring the sewers of New York at one point and I subtly amped up a heart beat ambience sound while describing the walls first starting to bleed and then pulsing... They found some of the equipment of the fellow they were searching and the sewage started to ripple as if something was about to emerge. They grabbed the gear and ran without seeing what it even was...

 

[Blackrat]

In the same game I had some living statues. As in a vampire had enslaved some athletes, painted them white and then used magic to make them stand still in poses like old greek statues. Only to move to defend his sanctuary. They were very much avare the whole time and as such driven quite mad by staying still for years on end...

 

[Stormonu]

Not mine, but a fellow 4E DM's:

Magic items in 4E are empowered by a magical substance known as Residuum. Our party was sent by the king to a nearby gnomish enclave to investigate the disappearance of several gnomes and the slowing of the Residuum trade. After several encounters with gnome bandits trying to drive us out, we soon learned the truth - the gnomish royalty was behind the abductions and were in fact attempting to conceal the truth that Residuum was actually created by an alchemical process used on the overcrowded gnomish population that distilled lesser (unwanted) gnomes into the magical substance.

"Residuum is made of gnomes!" was the resounding cry that went up from our party as we finally revealed the plot.

 

[Shiroiken]

The most gruesome thing I used was actually from the setting. In Rokugan there's something called the Living Darkness, the last remnant of the Nothing that was the universe before time. It's sentient with the goal of returning everything to the Nothing by consuming things, especially creatures. It's unrelenting, never stopping until it consumes everyone that learns of its existence. It's a campaign killer, since the PCs can't ever stop it, they can only escape and delay.

This campaign (one of my best) ended as a tragedy, as it slowly hunted down the party. In their home base, it sought out each PC to prey on their weakness, but each time giving a hint of their true target: the wife of their lord. One by one the PCs were either killed or consumed, with one managing to escape with his son (betraying the party and his lord to flee). The last PC managed to overcome his trap with the aid of his dead brother's spirit, but misunderstood the hint, believing the target to be his lord. He searched for the party to aid him, but found only bodies. He then went to his beloved, the lord's wife (who used to be a PC), hoping that her Void magic could hold it at bay. He came in as she was being consumed, and realized that if it obtained her magic, it would be immune to it forever. He went up and cut her down before she could be consumed, only to have guards come in soon after. He ritually committed suicide for his crime, ending the campaign.

A flesh golem made entirely of children.

One PC once made his exit from the campaign by getting flushed down an orc toilet.

Another time, members of the party were exploring a Necropolis and fell into a pit of infant zombies.

Oh and once, while the PCs were paralyzed and helpless, a half-fiend gnome pried open the skull of a beloved NPC and scooped out his brain to eat some.

I love the way you guys evil!

Sometimes it is the little things.

Absolutely! I took over GMing a group and ran a similar adventure to one run by the prior GM, where they had to enter the lands of darkness, which can corrupt the soul in addition to killing the body. Afterwards everyone talked about how terrifying it was, especially after the death of a PC. The other GM claimed I must have modified the monsters, and I explained that I hadn't. I just used better descriptions to provide a greater sense of dread, whereas he was fairly vanilla. The PC who died ran ahead of the party to fight two ogres by himself, in a game system that can kill you in 1-2 hits, so he deserved being squashed to a pulp!