I have run into some enemies (bosses mby ?) that have been curse immun - i assume.
Right now i don’t know if “mark of Death” gets applied to the enemy and it’s a visual bug; or if the enemy curse-immun.
I would suggest:
1: Add Curse-immun" tag to enemies.
2: A visual confirmation - “Immun” feedback when trying to apply a curse (Like when enemies “Dodge” an attack)