Diverse Face Shape
Your face draws immediate attention. It isn’t within the typical range of shapes of your ancestry. Part of your skull didn’t grow like skulls usually do due to the bones fusing, growing at different rates or some other cause. Consequently, when people who don’t know you see you, they usually only see your face . This gives you +(IE) to Dexterity (Sleight of Hand) checks but −(IE) (up to −4) to disguise checks or Dexterity (Stealth) checks to blend into a crowd as well as a −(IE) penalty on Charisma (Persuasion) checks due to many people’s discomfort around those with unexpected appearances. Note however that some facial differences can give you a bonus on Charisma (Persuasion) or Charisma (Deception) checks instead, such as your face being seen as cute or more like a local ancestry.
Note that this is usually a permanent condition and does not fluctuate, but the player and GM are welcome to determine a magical version that fluctuates based on the Frequency table. Classic stimuli include sunrise/sunset, fluctuation of the moon, or stress.
Real-world Examples
Craniosynostosis, Hemifacial Microsomia, Plagiocephaly, Macrocephaly, Microcephaly, Agnathia, Down Syndrome, Hydrocephalus
Assistive Options
Characters can attempt to use a Disguise Kit (with penalties per Extent) or some kind of hood or helmet to cover their shape if they’re trying to blend in, but otherwise, unless they have other traits, this trait by itself is cosmetic.