Entombed alive yet I survived

To glimpse once again at the sun

But legs to ground are shackled down

Curtailing all efforts to run

In body lies a dozen knives

My crown’s sure to split and to smell

A robber’s spear flew by my ear

Be thankful this ended so well

I read this riddle online, the answer to it is:

but i can’t understand why this is the answer, can anyone explain?