Filling out a poem with challenges

I'm hyperfocused on a poem(?) right now, and i wanna create a small homebrew adventure for my players after abomination vaults. modelled after the harrow world adventure from pf1e, and maybe a lil simmilar to Curse of Strahd. as in: every line of the poem marks a challenge the players have to complete before the final boss (im thinking a powerful Zealot of Groetus, bringing the end times closer)

So:

"Bring me midnight, the endless dark" -> No idea for a challenge here. maybe just make the world/demiplane very dark and broody?
"Bring me Beasts that howl and bark" -> Werewolves
"Bring me crimson liquid red" -> Vampires
"Bring me the sickness terror bred" -> No idea, i need help tp find somehting fitting
"Bring me lighting, terror true" -> Thunderbird
"Bring me hope of nothing new" -> This is where the party fits into the world, no challenge needed here
"Rot, decay, dilapidation" -> No idea
"Bring the end of all creation" -> gotta be the final boss, mid ritual to Groetus

toughts? Any recommendations for "The sickness terror bred" and "Rot, decay, dilapidation"?