The Plague is a Underland sickness first introduced in Gregor and the Curse of the Warmbloods. The plague only affects warmblood creatures and so is named the curse of the warmbloods. A troup of characters, including Gregor, Boots, Temp, and Ripred must journey to a field in which the said cure of the plague grows. Once they are there the group is attacked by giant ants and several dye, including Frill and Hamlet. The remaining survivers then conclude that D.r Nevive, who is supposedly the main leader in developing a cure for the plague is actually the scientist in head of creating the sickness, along with Solovet, to use as a weapon against the Gnawers. While Ares, Gregors bond, was visiting the developing lab he accidentaly knocked over a jar containing plague infected fleas. This, the p