Hello there !
I’m very excited to enter this excellent challenge. I will create a death/darkness Demon Lord called Smrttogoth. Strange name indeed, it’s a silly trick with the world ‘death’ in croatian, ‘god’ in german and a demonistic suffix.
I noticed that quite a lot of demonic creatures had 3 heads: Cerberus, Asmodeus, Balam… After few thoughts i decided to create a winged creature with 3 birds heads: a vulture and an crow head, but with 3 orbits for 2 skulls, like a malformation. This represents death, necrophagia, punishment of the dead ones, humiliation…
The other - and for now biggest one - is an eagle head wich represent the inevitable authority of death, majesty, the power and the accuracy of the bird of prey.
After a few messy sketches and the listening of obscure death, black and doom metal, i got this first interesting rough sketch.
I will see how i’ll find this after a sleep. Moreover, i have to add some clothes, armor, etc to show that it’s an intelligent creature.
On a battlefield, Smrttogoth is one of the most deadly Demon Lords. Flying over the enemy, he terrorize his enemies with his grim and unbearably loud shrieks. Some of the foes will panic, running like a scare animal with no place to hide. Some will be petrified by the sight of this giant winged atrocity in the bleak sky. To finish them Smrttogoth can crush his enemies, diving from the sky, shred them with his long claws, or use his most deadly power: the plague shriek. Accumulating a sphere of space/time abberation in front of his beaks, he spread it over 500m with a powerfull wing flap, causing on enemies the damages that 666 years in rot should do.

Good luck for the contest !
It looks slightly disturbing but i dont see it as frightening or as dangerous as a demon lord. Also maybe you locked yourself in to much to begin with, I’d like to see you experimenting with shapes alot more and not just, “hmm, i might add an arm there”. Maybe even forget about the figures and parts you are dealing with for a while and just play with some abstrakt forms, then you can transfer anything cool you might come up with into a more figurative form. Also you maybe should think about pumping up its scare-factor, if its a demon lord make it look superior and intimidating. Just some thoughts… Good start, really, but i think it be good if you let loose some more with your concept before delving into modelling. Keep it up m8! 