So, here is an answer.
- It is an uncommon loot on Byg Byrd - a shared loot mob, that has AOE damage, and quite alot HP (100k).
You can find them NE from Carnap's Landing TP on Land Area.
There are guys killing it alone, but i would advice to get a group of 5 mid level people, to make it easier.
- Event mobs, like Jolly Swamplurker or Jolly Jellyworm can drop it as well. They come in various hp and difficulty levels.
- Spawned / summoned with Totem mobs have a chance of looting it also, but it is a rare loot there.
To be able to spawn them, you need to have at least 200 ARC Badges with you, and a Totem ofc. ARC Badges come from HERE.
- And ofc there is an NPC Rudolf, located close to Turrelion/Rift wave spawn. He can summon a Jellyworm if you pay him 2000 shrapnel. Jelly is easy to kill, can loot Holiday Macic too, and after u kill it, u get 10 Magic as a reward.