Royal Jelly is a miscellaneous item that instantly adds 6 HP to the Spelunker's health when collected.
It can be found in a few ways. First, and most commonly, by killing a Queen Bee, which can be found inside bee hives in the Jungle. It can also be bought from Tun's shops for 23,400 gold (fact-check needed), found rarely inside of a present, or be gifted to you by Kali if you already have the Kapala every eight favor points