The wuggly-umps are a rare spawn, with unknown conditions to trigger them. When they are around, you can find them all over Alyria, SUG and the underground--they tend to cluster together and spawn in many zones, so happy hunting! If your character is at least 6 real life years old or was created [In Antiquity], you are eligible for this mark.
The mark is random chance and can take many kills to trigger mark completion. An immortal stated '100 is a reasonable average for that mark' to give a rough reference to how long you may take to get the mark.
Rewards: 7500 AP & 3 Vandy orbs