So, I got a little different interpretation of this from Austin (probably due to my own life experience and the existential dread I have rn) about this being about existential dread.
"God has forgotten about lonely spirits falling into velvet eyes"
Reminds me of a cruel world, as if abandoned by god, with no meaning or good left in it, velvet eyes, symbolising deep sadness or suffering but in a sophisticated way
I looked up symbolism for onyx, it turns out it's a symbol for strength and protection, and even a symbol for strength is crying, makes me think of even strong wills and spirits of people breaking at the hands of this cruel world, or maybe even god (the protector) crying at what his creation has become
light is not far but just far enough, suffering is too great and too prolonged to hold onto hope any longer.
A voice from suffering calls out to suggest death as a solution, almost solitude from this living hell. Even Jesus died for a higher purpose, maybe it is the right choice.
Thorns on the head have dug in so deep that they have melted in and blended with the blood, the pain being too embedded and intrinsic, changing a possibly hopeful and optimistic person into something terrible, which they loathe.
Shadowless church did come across as a place of worship devoid of warmth, but shadows don't really represent warmth, so I felt shadowless actually refers to no darkness anymore, just light, which is only possible in heaven, and this goes well with the later lines about blue skies above and bells of death.
So the speaker thinks the only place left to seek refuge is the church of heaven without any darkness, and in the eternal time there (golden sands), they will truly be able to live (because living to them has become akin to death because of their hopeless despair and a lack of a way out)
The darkness calls one final time towards death, the deep wounds of the person urge them to take this step into the void, and finally ascending from this hell,