Part of the Tentacled Beast is hidden underwater, with only its head and tentacles sticking out. The Tentacled Beast is entirely blue, almost matching the same shade as the water. It has four yellow eyes; there are two larger ones at the bottom and two smaller ones at the top. Part of the mouth peeks out of the water. Teeth can be seen bordering the mouth.
The Tentacled Beast resides in an area in Trohn accessible via a hole that is blocked off by a blue lock. After obtaining a blue key, the player can take the seedling to unlock the blue lock and fall down the hole. It is found in a mostly open area of water, with two waterfalls on either side of the wall.
The Tentacled Beast attacks by raising its tentacles out of the water. It will wave them around for a couple of seconds before returning them underwater. The tentacles move to various places around the area in an unpredictable formation.
As the Tentacled Beast attacks, whirlpools are also created. The player must be wary of these as the young seedling will be drawn into them and instantly lose all his lives. The gradual fade in to the water signals the coming of a whirlpool, as they also appear in random formations.
To defeat it, the young seedling has to use his sword or Wand to hit all the tentacles. To avoid the whirlpools, he can go inside the Tentacled Beast's mouth, as no tentacles or whirlpools rise up from under there. Each tentacle takes one hit from a sword.
Once all tentacles are cut, the Tentacled Beast is defeated. All whirlpools will stop in the water, and the young seedling can proceed to go inside its mouth, where the Tentacled Beast dweller is met.