My main inspiration for my monster designs is the dark souls series and bloodborne as they have very interesting monster designs especially the boss battles like the Cleric Beast, The Blood Starved Beast, The Watch Dogs of The Old Lord, Great Grey Wolf Sif, and my favorite Ludwig The Accursed/The Holy Blade
This one was more based on the hollowed enemies in dark souls except if one of them got juiced up by killing everyone and now he's the boss on top of a cathedral that happens way later in my story.
This design took ques from Bloodborne by the Cleric Beast and I took my own spin on it by making it look like it has been through hell and back as its organs and bones are exposed, it's skin is torn apart, its head is cracked opened exposing the brain with the eye imbed in it, and its carrying its own still-beating heart. This one also has yet to appear in my series but when he does he oozes with terror.