
You see a magic pillar.
Notes
After Ferumbras death, there will be Demons in his room. These demonic beings are summoned by Magic Pillars.
Abilities
Damage Taken From Elements
Physical 
Death 
Holy 
Ice 
Fire 
Energy 
Earth 
Drown 
Location
Behaviour
Magic Pillars are unable to move. They don't harm you, but their summons do.
Strategy
Just kill the Demons or run away from them.