Symbiotic Jelly

A far-off relative of the gelatinous cube, the symbiotic jelly is only 2-3 inches across, a yellowish, jellyfish-like blob, round or slightly flattened, translucent and faintly milky with no fixed internal structure. About three dozen fine tendrils radiate from it, serving as antennae through which it reaches and controls another creature's mind.

The jelly settles in an empty cave and sticks to a shadowed spot on the ceiling, where it is nearly impossible to spot. When a carnivore wanders in, the jelly uses innate charm monster to telepathically urge it to stay and attack anything else that enters. It ignores non-carnivores, undead and creatures native to other planes.

Next it weaves a pair of vivid illusions, much like a veil spell. One makes its charmed guardian look like a far feebler version of itself; the other conjures enticing false treasure deeper in the cave. Using an ESP-like power, it reads each newcomer's desires to choose the bait, and watches their reactions to adjust both illusions in a split second, too fast for viewers to notice. Everyone but the charmed beast accepts the illusions as real unless a save vs. spell, made at -7, sees through them. So a massive cave bear might seem a scrawny cub, while deeper in, a dwarf glimpses a rich gold seam and a hungry halfling sees a banquet.

Its control tendrils are delicate but regrow within 1-3 turns each. Every lost tendril adds a matching chance that the link to the host breaks: with 6 of 36 destroyed, there is a 1 in 6 chance the jelly loses control.

The jelly feeds by draining energy from its carnivore host while the host eats, from about ten feet away. If the guardian kills an intruder, the jelly feeds through it during the meal; if the guardian loses, the jelly tries to charm the winner as a replacement. Sages think it actually feeds on the emotional satisfaction of the predator's hunger.

After a month without food it seals itself in a protective shell and goes dormant until a new carnivore arrives and the charming can start again. A jelly paired with a cave bear therefore sleeps through the winter alongside its hibernating host.

Symbiotic jellies are very rare and poorly understood, and their role in the local ecosystem is unknown. Their intelligence is instinctive rather than learned. They have few known commercial or magical uses, though their distilled essence may help in brewing potions that mimic their symbiotic way of life.