Tentacle

Tentacle=

Big Tentacle=

Baby Tentacle=

"I'm glad the rest of it is still down there."

- Maxwell

Tentacles are hostile Monsters that specifically spawn in Marshes or Caves, though they will not spawn on world-generated roads. Wickerbottom can summon Tentacles using On Tentacles, one of her self-published books.

When the player or mob gets close enough to the spawn area of a Tentacle, bubbles will appear on the ground. Then it will appear as a purple, spotted tentacle, spiked at the tip, which will emit growls and come out of the ground to attack anything that comes close enough.

Tentacles take three blasts from the Ice Staff to be frozen and cannot be put to sleep or set on fire. When killed, they will drop 2 Monster Meat and can drop a Tentacle Spike or Tentacle Spots.

Big Tentacle
A Big Tentacle, also known as a Tentapillar, is a large section of Tentacle that appears underground, going up toward the surface. Attacking it will cause several, smaller "Baby" Tentacles to spawn around it, which will focus their attack on the player, but are weak and will die from one hit from a Spear. When defeated, the Big Tentacle will retreat into its hole, causing an Earthquake and dropping a variety of items, some of which are limited to a number per day across all Big Tentacles.

When it retreats into its hole in DST, the earthquake won't happen, nor it will drop items. Instead, the player can travel through the hole, just like a wormhole, Teleporting them near another big tentacle.

Baby Tentacle
Whenever a Big Tentacle is attacked, it will spawn several "Baby" Tentacles, with every hit on the Big Tentacle spawning groups of them at a time. These tentacles are smaller than regular Tentacles and only take one hit from most weapons to be killed. They do not drop anything, as they are there only to protect the Big Tentacle. They also lack the spikes that the regular Tentacles have, though they still sport the telltale bumps in the ground when they're about to come out.

If the Big Tentacle and the Baby Tentacles aren't attacked for a while, the small ones eventually retreat back into the ground. Baby Tentacles are only found underground.

Baby Tentacles will fight nearby Tentacles and vice-versa.

Behavior
Tentacles are very dangerous because of their high damage and high health. A careless player might walk straight into an area with many Tentacles and get stun locked long enough to be killed. They can only be seen once a creature or player gets relatively close.

At first, there will be a barely noticeable bubbling patch on the ground, followed by a piece of tentacle that looks like a purple bubble, which appears just before the Tentacle appears. When a creature is in range, the Tentacle will emerge and twirl around once before snapping and standing straight up. There is a brief delay before it will strike again.

As long as its current target is still in range, Tentacle will not change targets even something else attacks them, similar to Tallbird.

If its target moves out of range, the Tentacle will sink back down into the ground; it cannot move around or give chase. After going back underground, Tentacles will stay hidden until another target moves into range or directly hits them, at which point they begin to attack again.

Due to their aggressive nature, it is common to find drops from creatures they kill or from dead Tentacles killed by other creatures (usually Merms) lying on the Swamps. They can kill a group of 4 Spiders on their own, many times, though it depends on the situation. Due to this behavior, many players like to use Tentacles as a type of food and item supplier, especially if they are camping in or near a Marsh.

Even though Tentacles do not respawn, the player can still get the loot normal Tentacles drop via Big Tentacles. Therefore, if one is using a Tentacle as a food and item supplier, this could prove a problem when the Tentacles near Rundown Houses or Spider Dens inevitably become extinct.

Wickerbottom is the only character who can have the ability to stop Tentacles from becoming extinct, since On Tentacles is crafted with Tentacle Spots and Papyrus, which as said above, can be obtained from Big Tentacles and Papyrus is easily crafted using the Reeds found in a Swamp.

Hunting
Tentacles cannot be stun locked. With most characters, it takes 15 strikes with a Spear to kill one. If properly timed, they can be attacked in between their strikes. Although they appear to have an area attack, Tentacles actually attack targets individually. Due to this limitation, Pigs that attack if they get too close can easily kill a Tentacle if there are at least three of them.

Tentacles will still produce an Insanity aura, even if it is still in the ground and out of attack range. Thus, the sanity meter is a good indication that a Tentacle is near. Additionally, there is a low growl that can be heard when a Tentacle is near, and the player can watch for the bubbling patch, though Sanity drain is still the best indication, as the Tentacle growl can easily get confused with the normal growling ambiance of the swamp. During Adventure Mode, the sanity meter indication can be a life saver if the player is traveling in a swamp at dusk or night.

A safe, but time-consuming way to fight a Tentacle is to go right next to the spot where the Tentacle will come out, hit it as soon as the little nub appears, and dash to the side, out of its reach. Repeat after the Tentacle retracts into the ground.

It can be easy to kill Tentacles with little to no work by finding some Rundown Houses, waiting for Dusk, and seeing if the Tentacle alarms the Merms. The stiff fight will end in Frog Legs, Monster Meat, Fish, and perhaps Tentacle Spots, or a Tentacle Spike.

To make "tentacle traps", the player must bring several Pine Cones to the swamp and plant 3-6 of them around where the Tentacle emerges. Once the trees are grown and the player is ready to harvest the tentacle, they can simply light the trees on fire and the tentacle will die before the last tree burns out, even when hidden underground. The downside is that any Tentacle Spots that drop will also burn leaving only Ashes. This method of hunting is easiest with Willow due to her fire affinity.

Alternatively to the method above, one can use Gunpowder. A player can place a stack of three near a tentacle, ignite them and dash away. Even when hidden underground the tentacle will die instantly in the blast. A gunpowder stack of two can also be used, but the tentacle will need to be finished off with 2 swings of a Tentacle Spike. The player is usually fast enough to kill it before it manages to attack in this case. However, this case would require 3 consecutive swings of the Spear, which will allow for retaliation after the second swing.

Below is the number of hits it takes with each weapon to kill Tentacles when playing with characters with a default damage modifier. The Weather Pain is not included due to the random nature of its projectile.

Trivia

 * If the player is near a Swamp biome, the Tentacle can appear (barely) outside of its biome.
 * When using the Thulecite Club, there is a chance that small Shadow Tentacles will appear and assist the player with attacking.
 * Maxwell expresses surprise at the existence of the Big Tentacle and the baby Tentacles, suggesting that the Tentacles are reproducing, and were not planned to do so, as Wilson and Wickerbottom mention that Tentacle Spots are its genitalia; supported by Maxwell's quote for Tentacle Spots, 'This is how they reproduce'.
 * The small tentacles that appear around the Big Tentacle used to be colored green.
 * In the script that handles the Tentapillar's emergence when the hole is attacked, there is a note/Easter Egg that says: ("Hit calls cthulhu"). This is a reference to a story by H.P. Lovecraft called "The Call of Cthulhu".
 * The script refers to the "baby tentacles" as arms, suggesting they are from the same entity.

Gallery
Tentakel