Answer:
A muttered rumble was heard from the pen, and I, in my walking stopped to look in. What was this I saw? A massive beast, hoofed, and jawed. With spikes upon its mighty brow, I watched as he struck the turf and prowled. And yet for all of his magnificence, he couldn't get out of that wooden fence.
What is the heart of many risks, has a heart, but is not a living being?
Fuels backyard get-togethers
As soft as silk, as white as milk, as bitter as gall, a thick green wall, and a green coat covers me all.
Stealthy as a shadow in the dead of night, cunning but affectionate if given a bite. Never owned but often loved. At my sport considered cruel, but that's because you never know me at all.
People take me on walks and I run and have fun. What am I?