An older picture of Mala, one of the first I drew.

Mala is the manifestation of humanity's negative emotions and thoughts. Normally she inhabits just the minds of each individual on Earth, but if enough people feel a large amount of negative emotions all at once she can be summoned into an actual physical form. She cannot exist in the real world along side humans, she already exists within them, but in afterlife realms or alternate dimensions where humans are present she can take form. The only exception to this is when something truly horrific happens on a site in the physical world. Mala can feed off of the lasting residual suffering and exist as ghost of sorts, causing living humans who come to those places to feel uneasy or hear her whispers.