On dDark sStormy nNights On Dark Stormy Nights

Capitalize important words in titles

On dark, stormy nights, I wake up with a shriek as the white Beast pounces on my chest; its sharp claws digging into my flesh. On dark, stormy nights, I wake up with a shriek as the white Beast pounces on my chest; its sharp claws digging into my flesh.

Knowing it has got my full attention, the Beast rises and becksummons me to the altar. Knowing it has my full attention, the Beast rises and summons me to the altar.

"Beckon" is a gesture with the hand. I imagine your Beast meows imperiously, as mine does. "Summons" fits more with the mood you're going for as well as with the actual abilities of the cat.

In a trance-like state, I rise up and proceed to make an offering of ground bones and dead meat, as I knowing it to be the only way out of this nightmare that has befallen upon me. In a trance-like state, I rise up and proceed to make an offering of ground bones and dead meat, knowing it to be the only way out of this nightmare that has befallen upon me.

Not incorrect, just thought it sounded more poetic this way. That is entirely subjective though.

In a trance-like state, I rise up and proceed to make an offering of ground bones and dead meat, as -- I know it to befrom experience that it is the only way out of this nightmare that has befallen upon me. In a trance-like state, I rise up and make an offering of ground bones and dead meat -- I know from experience that it is the only way out of this nightmare that has befallen upon me.

Your basic command of English is quite good and you write with charm and fluidity. So, I am being pickier. I would also suggest that the second half could read "... that it is the only thing I can do to appease the Beast."