Unnatural Aura (3.5e Trait)
From D&D Wiki
Your growth has been tainted by a strange creepiness that scares others. While some creatures barely notice your aura, others are sensitive to it and find it disturbing and threatening.
Benefit: Your unnatural aura grants you a +2 bonus on Intimidate checks and to the DCs of any effects you have that possess the Fear descriptor.
Drawback: Your unnatural aura disturbs people and animals, imposing a -2 penalty on all Diplomacy, Handle Animal, and Wild Empathy checks you make.
Roleplaying Ideas: Characters with this trait might be brooding loners, constantly walking apart from their friends and comrades and cursing their solitude, or they might delight in the fear they cause, taking opportunities to scare others at every chance.