Jabba’s are paranormal monsters named after the infamous Star Wars character Jabba The Hutt. These relatively new Cryptids first began to appear in the 1950’s, and were merely classified as large scale cannibalistic Shape Shifters for a time until given the name Jabba in the mid 1980’s. These are humans with a unique set of junk DNA. Those usually responsible for superpowers in Humans. These genes appear to interact with a combination of environmental pollutants such as radiation, and various chemicals including unnatural food additives. Soon after genetic activation the human subject acquires a monumental appetite despite having a low metabolism. They quickly pack on the pounds, and at some point they set their eyes on small humans. Upon their first foray into cannibalism they begin to develop shape shifting properties that allow them to devour large items they can swallow whole. They can literally stretch their mouths, and digestive systems to accommodate all manner of objects including furniture, and sometimes small vehicles! However they primarily crave humans in an almost zombie way. They retain their sentient intelligence, and are alive so they are by no means zombies. Although their persona is obsessed with devouring everything in sight! In addition even if these cannibalistic sickos get so desperate as to start eating corpses they won’t turn into Ghouls.
The Jabba’s eventually bloat up to several tons or more in weight. Their natural state is a grotesque blob of deformed blubber who limbs are barely
Cryptozoologists have yet to find the specific set of mechanisms that cause Jabbaism nor the cure. However if caught, and supernaturally treated in 
Jabba’s aren’t demonic in nature so religious artifacts have no effect. For reasons unknown they seem to be immune to even the most magnificent magics. Possibly some protection caused by a direct tapping into the supernatural human soul? If they don’t eat you whole then they’ll simply sit on you causing you to literally flatten like a pancake! Your only defense is to run because that they don’t do very well moving fast even in their brief human forms. That mass is still with them. It’s just extremely tight packed into their compact form. Paranormal professionals have been able to capture, and contain Jabba’s in their hibernation state with the element of surprise, and special heavy lifting equipment of steel. There are at least three live specimens currently locked away in secret underground supernatural facilities around the world. Study continues into these deeply disturbing supernatural oddities!
Is there any way to kill them other than their natural Death? What if someone be heads them In their Ugly blob form? Them burning their remains with normal, holy, or unholy fire?
Also do they have worm like tails?
No they’re just uneven blubber blobs but since they’re Shapeshifters they could form a tail if they wanted to.
We just don’t know. Nobody has been able to behead or burn one yet. I suppose if one could be thrown into some kind of giant industrial shredder there would be a chance. Fire of any type doesn’t do much. The blubber is simply too prolific to be believed. Holy or Unholy is irrelevant as they are basically a mutated human.
Are they even immune to hyper magic Omnimagic or macromagic?
I would think not. However it’s beyond rare for anyone to practice true Omnimagic, and Macromagic so we can’t say for sure.