Sorry for any confusion this may have caused!
Is the entity weak to light?
One thing I've noticed is that there's a lot of things to suggest the entity is weak to light, such as the killers that were given gifts by the entity (wraith, hag, nurse, spirit) All have some major weakness to flashlights, and usually pertaining to the ability given to them by the entity. Wraith is stunned by flashlights while invisible, blinding nurse while she is charging a blink fatigues her, flashlights destroy the hags traps, (and although this was a bug) you could instantly blind spirit with flashlights. Also, since the red stain appears to be from the entity watching the match play out through the killers eyes, (that would also explain the weird black border around your screen while playing killer) that would be why flashlights stun killers so much, causing them to drop bodies as if they were hurt, because you are shining a light on the entity itself. This is also why generators would open the exit gates, the light weakens the entity enough that you can escape, at least from that trial. Would this would also be why after you've completed a few the hatch can open? I remember the devs saying somewhere the hatch wasn't made by the entity, so maybe by completing generators you produce enough light to weaken the entity enough to where it can't stop the hatch from appearing?