A nasty, contagious, non-curable debuff the factions banned years ago, causing insanity, rabies, and bloody death.
Baroness Victory describes the Gurgles as a really nasty, contagious, non-curable debuff that the factions agreed many years ago never to use again because it is so insidious. It is the source of the Insanity and rabies debuffs afflicting the Juiced Rot Sticker Behemoth pets — victims spew blood from mouth and eyes and turn on their own side.
At the Southern Front, The Reavers infect their pets before the magic ban takes effect, making its use technically an exploit rather than a violation; a soldier notes the system has allowed such iffy workarounds in the past and that the defending mages simply need to keep infections from sneaking in. When gurglers reach the trench, an elf flees a pack of about ten infected veterans; a mage fills that trench section with dirt and the crawler Kristen Cronin bakes the emerging limbs with a flamethrower, then sits down and sobs, protesting that the Gurgles is a magical attack and should be banned.
The banned biological weapon that turns crawler soldiers into contagious berserkers inside their own trenches.