Rancid Rat

Rancid Rats are small rat-like enemies. They appear as large, purple rats with glowing peach eyes, and multiple large orange tumors growing on their backs. They are found in several locations in large numbers alongside other enemies.

Behavior
Rancid Rats usually appear in packs of 2 to 3, often with another enemy. They attack the player once they are within attack range.

Strategy
Rancid Rats have low HP, and a single attack or two, or even a ground slam from longer heights, will easily dispatch them, There's always the option to use AoE active skills if you need to kill them quickly.

Generally speaking, the Rats should be the first things you kill when engaging an enemy pack, not only because they're the quickest to kill, but also because their attacks are surprisingly tricky to avoid, as it covers a fair amount of distance. Sometimes rolling away might not be good enough to dodge it if you do it too early. They can be especially annoying if your only weapon is a projectile without piercing, since they can absorb shots that are meant to hit something else. As long as you kill the Rats before they can react, they should pose very little threat.

Trivia

 * They were added added in v1.8, the Bestiary Update.