Smoke and Darkness

I walked through the dark, damp, cold cave
As I walked further I heard a deep breathing like that of a knave
Then I realized something was glistening ahead
And I found a large creature upon a bed
I wondered what this huge beast could be
Stepping into the light, so as to see
I saw the glittering things
They looked like huge diamonds fit for kings
These beautiful things formed what looked like fish skin
Except they were much brighter than any other fin
I was quite happy that the eyes were shut
For the teeth and claws could easily cut
I saw the most enormous bat wings
And a spiky tail that could give a million bee stings
Suddenly the great animal stirred
Then a sound came out of it, it purred
But not as a cat, the sound was as loud as the bursting of a thousand kegs
And it sprung upon its great hind legs
Then the monster opened its jaws
Smoke escaped and it reached out its claws
I turned and fled this wild beast
For I certainly wasn't going to be its feast
Still to this day I wonder what it was again and again
Do you know what it many have been?