A man suffering from a powerful curse, turned into a monster

A great mount from the wizard's city of Dragongrave

A tree bearing sickening fruit, a thing of horror turning its victims into undead servants.

Strange plant-like creatures that many believe immigrated from the Moon to the Earth

There are few horrors starker than meeting a wormspawn, perhaps meeting one wearing your face is the worst

We made a mistake, we assumed they were normal goblins, short and cranky as they were. We thought the horns were some sort of decoration or one of their fetishes. The horns were attached and they were much more than mundane grots. They were hell grots. 

also known as slaughterbots, or lethal autonomous weapons

Contrary to the name, a bimbo bot is not a machine, it is something much worse.

Adding a little unexpected to your magic bag of critters or the like.

Where came the sickness, the shaman knew not. No herb, no smoke, no spirit dance could carry it away. What curse of heaven carried the plague, the sages and priests could not say. The gods struck, and no prayer, no elixir could save their victims. How the malaise spread, no doctor could know. With not even a body to spread the miasma, surely it must be a curse. And when at last, the right lenses were turned upon the pus of the suffering.  

The Usagin is a high end biomod that is a popular niche product in the Cosmic Era. The dedication required to become a bunnyperson is serious, as some of the mods are invasive and make some common tech devices no longer operational for the usagin.

A way to increase the danger of a monster through an unusual mechanic

An ancient race of nearly-humanoid spiders that have lived on the fringes of civilization for as long as recorded history.

Gijinkagrams are a niche anomaly in the Cosmic Era, and they can be eliminated by routine maintenance on high end electronic systems. 

"AAAAAAHH, it's a troll!"
"Protect the women and children! Grab your torches!"

"AAAAAAHH, it's a troll!"
"****head... we banned him five times and he keeps making new accounts about how he pwns all and that he>>>>>>>>>>>>>>>>>>>j00!"

The most common domestic companion animal of the Kel'Regar, the Kel'Mestath has been bred into a wide variety of sizes and roles. Humans and their allied species often think of them as similar to cats or dogs, a perspective that the Kel usually encourage, for the full understanding of the Mestath tends to cause a certain level of discomfort in many aliens, but especially that close ally, humans.

An ethereal/astral parasite that feeds on emotion

also known as a great goblin, dread goblin, or super goblin

A highly transient form of digital life

A slowly growing bomb in the CogNet