The bubble on its body keeps getting larger, and, in the end, the poison squirts out from it. If the Mongolian death worm is real, it's highly unlikely that it is literally a worm. Annelids and similar invertebrates are unable to survive in a brutally hot and dry climate like the Gobi desert, because their bodies cannot retain moisture and they would rapidly die of dessication. It has been suggested that Allghoi khorkhoi might be a worm that has adapted some sort of cuticle membrane to hold in moisture, but a more reasonable candidate would be a snake or other reptile. Mackerle has posited that the creature might be a skink, a strange variety of lizard whose nondescript head is hard to distinguish from its tail.
Skinks also live buried under desert sands.
But they have four stubby legs and scales, unlike the reportedly smooth-bodied death worm. Mackerle has also suggested that it could be a type of lizard called the worm lizard, although that species is not poisonous. Among lizards, only the Mexican beaded lizard and the gila monster possess poisonous venom, but they do not squirt it, and their venom definitely is not instantly lethal on contact. Another possibility is that the death worm is a member of the cobra family called the death adder. This species has an appearance similar to the descriptions of the Allghoi khorkhoi, and it does spray its venom.