It is actually a clay model of a fish with 13 wooden dorsal spines. The dancer experiences terrible agony, writhing on the ground. The whole ritual ends sadly with a death song. The fish involved in the dance is the stonefish, also a member of the scorpionfish family. It is believed to be the deadliest fish in the world. 

This is the most venomous fish known. It reaches up to 35 cm in length and lives in the Indo-Pacific region and northern Australian waters, from Brisbane to 600 km north of Perth. Stonefish may be found from exposed sand and mud in tidal inlets to depths of 40 m. Lying on the sea bed, it is perfectly camouflaged and looks exactly like an encrusted rock. It feeds on small fish and shrimps. When they swim by, the stonefish opens its mouth with lightning speed and gulps them down. The whole attack lasts for just 0,015 seconds.

Because the stonefish is vulnerable to attacks by bottom-feeding sharks and rays, it has found a way to defend itself- there is a row of 13 venomous spines along its back. In fact, the victim is the one who injures oneself. The stonefish is only dangerous if stepped on or caught. The thirteen dorsal spines project from venom glands along the back and venom is involuntarily expelled when pressure is exercised upon them. Then, a few weeks pass before the glands regenerate and recharge.

The sting causes excruciating pain and a tremendous swelling rapidly develops with death of tissues. The severity of the symptoms depends on the depth of penetration and the number of spines involved. The effects of the venom are muscle weakness, temporary paralysis and shock, which may result in death if not treated. Fatalities are known in the Indo-Pacific region but not in Australian waters.

One can prevent oneself from stonefish injury by wearing thick-soled shoes and treading very lightly- spines can piece through a shoe!

First Aid
At the beginning immersing the stung area into hot water may be effective, but hospitalization for intravenous narcotic analgesia, local anaesthetic infiltration or regional block may be required. Definitive management consists of administration of stonefish antivenom usually given intramuscularly. 
Antivenom is administered if:
-the victim suffers from severe pain
-systematic symptoms like weakness and paralysis are observed
-there are multiple punctures, which indicate the discharge of several spines. This means that larger amount of venom has been injected.