The Cavern Altar is a Mysterious Place containing aTalisman Fragment. The player is blocked from progressing by the Creepy Wriggly Monstrosity. On the other side of the monstrosity is a doorway.
In order to pass by the monstrosity, the player needs the Coconut Lantern. Once it is lit, the player can walk past the monstrosity and enter the Labyrinth. The Labyrinth contains fifteen rooms in total but only two with objects of interest: one with a Talisman Fragment and one with an Astral Branular Anomaly. A full map of the labyrinth with the location of each is below. Each room in the Labyrinth has a particular arrangement of short and tall doors which make it uniquely identifiable. These arrangements are duplicated in the map below so that you can always know where you are (click to see a larger version).
This map was created by doing a breadth-first search of the maze, starting at the entrance. Doors with colored dots next to them lead to doors on the same level with corresponding dots.