Despite being supreme ruler of all the jellyfish in that pond just outside of Godville, the Royal Jellyfish spends most of her day squirting out Royal Jelly that is often used as an aphrodisiac by misinformed heroes looking for a date with the trader's children. It can be sold at a relatively modest price assuming the trader is also modestly inebriated.
You can find this majestic creature wandering far from the ponds of Godville as she is quite fond of reminding everyone just how important she is.
The best thing way to defeat her is to tell her to go back into the kitchen and make you a peanut butter sandwich with; no jelly. This has a two-pronged effect of infuriating her feminist sensibilities while also insulting jellies everywhere. She somehow finds a way to feel personally insulted.
Heroes are advised not to approach her as she will attempt to make you her minion. Heroines are strongly advised not to make eye contact as she will attempt to start a lengthy conversation with you about the latest jellyfish trends and her many non-existing suitors.