

Light comes up from below the face, so the shadows rise upward. It is the opposite of normal sunlight, so the face looks strange and eerie.
Telling a scary story, the first reveal of a villain, when a phone, campfire or flashlight is below the face.
Public AI example available — The Melies 'Underlighting' page has a prompt example that names a light source under the chin. Camera presets do not apply (this is a lighting technique).
Underlighting, a girl telling ghost stories at a sleepover holds a candle under her chin, her face lit from below with upward shadows on the cheeks and nose, close-up, locked-off camera, 85mm lens, dark bedroom background, spooky playful mood, 5-second shot.
close-up of a man's face lit only from below by a phone screen at chest height, shadows climbing over his cheekbones and eye sockets, dark room, everything else black
Frankenstein (1931) — The monster is lit from below, so the shadows of the brow ridge and eye sockets look flipped (Melies). PremiumBeat also uses a Boris Karloff still from this film as an example of lighting from below.
PremiumBeat — Exploring the Emotion and Beauty Behind Uplighting