Primordial Malignity

I can feel the unseen horror and its forces closing in
Lurking at the threshold
Desperate to find a way to barricade the cosmic gate
I conjure a horrendous apparition
Looking for guidance, I speak:
The flesh is weak
My form is frail
Webbed with the signs of time
Since this frightful prophecy was first revealed to me
I request passage
Or a means of defence
This horrific oracle explains
The tools to bring defeat
Lay beneath my feet
My chamber built on
The roots of hidden ancients
As I tear into the earth
It bleeds clear
Vile and unclean
Primordial malignity
Agitated, it starts seeping into my body
I feel my limbs expand
Bones breaking and reforming
My flesh becomes oak
I am rooted into the ground
I stand as tall as the surrounding forest
I am impenetrable
But I am immobile