Giant Jellyfish

These huge relatives of the Portuguese man-o-war drift in warm seas at or just under the surface, trailing curtains of venomous tentacles. Some kinds are almost transparent and go unnoticed 90% of the time by anyone who cannot detect invisible things. Size depends on Hit Dice: each HD adds 2½ feet of diameter, 10 tentacles and 10 feet of tentacle length, from a 1 HD jellyfish 2½ feet across with ten 10-foot tentacles up to a 4 HD giant 10 feet across with forty tentacles hanging 40 feet down.

A man-o-war has no real control over where it goes, though it instinctively shrinks from pain. Touching a tentacle inflicts poison damage and requires a save vs. paralyzation; failure means paralysis lasting hours, during which the tentacles hoist the victim up and digest it over 3d4 turns. A single hit point of damage severs a tentacle without hurting the creature, and lost tentacles regrow in a few days; only blows to the body can kill it.

Adults drift alone on warm currents, though chance may bunch them together. They prefer tropical shallows and rarely sink below the sunlit depth of about 30-40 feet. Storms sometimes cast them ashore, where the tentacles lie half-buried and hard to spot, a cruel surprise for barefoot walkers or anyone digging in the sand, at least until crabs and seabirds finish them off.

Some small fish are immune to the venom and shelter among the tentacles, which tends to draw bigger predators to the jellyfish. Primitive tribes use the tentacles in simple traps or make crude whips of them that lose their potency quickly.

Sea swarms are great masses of young men-o-war found in tropical waters, drawn to light and vibration. A swarm counts as a single 2 HD creature, and very large gatherings may be several swarms. It makes one attack per round for 1d4 damage plus a save vs. paralyzation. Because swarms drift slowly and erratically, a creature rarely suffers more than one attack unless magic is steering them. They are too small to eat anything but tiny victims, though they scavenge scraps left by bigger predators. Aquatic monster summoning can call up a sea swarm.