The first curse was the dying words of King Gregs, who was usurped and kept in the castle dungeons and murdered by the wardens. So now the sun does not shine within the castle walls, from the outside it is as if the castle is within shadow, from the inside it is as if the whole world were night forever, sunlight simply does not enter the castle. Looking from the castle walls during the day is looking into a dark land, the castle is cold as winter, no plants grow, and fires are kept burning at all times for heat and light.
The curse of Prince Llolg, a rival of Solemn Cry, who was kept hostage in the prison from boyhood and died. His adult sisters, sorceresses from a western land, pronounced the curse. An immortal monster appeared in the castle. Like a dragon in appearance, but mucal and transparent, its slime corrodes, its wings cannot fly it, it is slow but cunning, and quick when hungry or malicious. It lives in the castle now and goes where it desires, and though when it grows too large the prison puts it to death (at great cost) it returns.
Then the curse of the sky. A stone fell and where it landed the ground was poisoned. Those who live in the castle too long begin to rot from the inside although their bodies seem to maintain consistency and health when they are cut open their bodies are filled with a pus. But the rock is beautiful and it is kept, according to the whims of Dendric Vast.
And Dendric Vast is insane and each day insists on new rules. And the prison is overflowing with the prisoners. And the central prison block has been added onto and added onto and no one person knows exactly what is inside anymore or how it is laid out or how deep the dungeons go. And it is forgotten who is kept prisoner, despite the efforts of the scribes, who toil to record their crimes. And the Prison Knights patrol the countryside searching for criminals, and they patrol the castle searching for criminals, and they patrol the prison searching for criminals. And the prisoners say that the true keepers of the castle are the blind medusa Malareth and Pallid Gross, Carnifex of the Church of Urizen, who are sequestered in opposite ends of the prison, and warring for control.