The Blargh is a creature found in the bellies of giant worms. When one worm is eaten by another the imps inside the worms battle for supremacy. The Blargh is essentially used as a living tank in these battles.
The Blargh is immune to magic and possesses significant strength due to its size.
Richard and Cale encounter it after the worm they are inside of is eaten by another. Richard decides to fight it by himself and gets knocked down by a punched before getting up. Afterwards, Richard sends it flying with an unknown attack and with enough force to go through the worm and kill a sand dragon on impact which also killed the Blargh.