Is it the will of the angels?

Season 4 of Shadowhunters. (Completed)

" - What are these tattoos on your neck?"

One touch, one question is sometimes enough to trigger something in yourself. Something from your past you forgot ever existed.

Dark forces are waking up from a long sleep, light forces are losing powers and the shadows are growing bigger than the light.

All the rules are broken. The night's children bring their darkness into the light, the servant of the darkness come to Earth and shadows follow them.
The fall of an angel weakened the Light's forces.

How will they fight the demon of the demons, the greater one who has ever existed without their own powers?