Pit Lord

Pit Lords are a type of megademon. These horrifying creatures are often entrusted with messages and assignments too important or sensitive for lesser beings.

In-game
Pit Lords are encountered in of Diablo II. One must be ready, for they claim their trophies with a sharp-edged black blade of disastrous power and their breath, being combustible in every gasp, can suddenly ignite into a blistering blast of flame similar to an Inferno spell. They can be found in Plains of Despair (Unique and Normal only) and are also usually seen patrolling the City of the Damned and occasionally step into the River of Flame (no Unique).

Trivia

 * Identically-named demons exist in the Warcraft series.