Mefitis

In Roman mythology, Mefitis (or Mephitis; Mefite in Italian) was a minor goddess of the poisonous gases emitted from the ground in swamps and volcanic vapors.

Mefitis was the Samnite and Oscian goddess of the foul-smelling gases of the earth, worshipped in central and southern Italy since before Roman times, with her main shrine at the volcano Ampsanctus in Samnium.

It is theorized that Mefitis was originally a goddess of underground sources, such as natural springs— the fact that many of these springs were sulfurous led to her association with noxious gases.

[5] Virgil describes this sanctuary in the Aeneid: In midst of Italy, well known to fame, There lies a lake (Amsanctus is the name) Below the lofty mounts: on either side Thick forests the forbidden entrance hide.

Full in the center of the sacred wood An arm arises of the Stygian flood, Which, breaking from beneath with bellowing sound, Whirls the black waves and rattling stones around.

Face of the goddess Mefitis, bronze fragment stored in the Museo Archeologico Nazionale della Basilicata (National Archaeological Museum of Basilicata), Potenza.
Ancient Roman votive offering such as would have been offered to the goddess