Treeguard

Treeguards are Monsters that can occasionally transform from Evergreens when a nearby Evergreen is chopped down. They are initially hostile towards the wood-cutter, have very high health and damage and are capable of killing an unarmored character in three strikes. Treeguards do not normally spawn before Day 3, after which each Evergreen felled has a 1.33% chance of spawning one. After Day 30 up to two Treeguards may spawn at once,  with up to 3 spawning after Day 80 given there are enough Evergreens nearby. They can spawn from any size Evergreen tree, besides Evergreen saplings (from recently planted Pine Cones) and Dead Evergreens. A special Set Piece can be found, called Living Forest as soon as Day 1. A Treeguard takes four blasts from the Ice Staff to be frozen. When killed, they drop Monster Meat and 6 Living Logs. Living Logs can help build a Shadow Manipulator, among other things.

Behavior
There are 3 sizes of Treeguards – short (70% scale), normal (100% scale), and tall (125% scale) that spawn from the respective size Evergreens. Their scale affects their health, damage, combat range, and walking speed. When they first appear Treeguards will aim to attack whoever chopped down trees near them and will follow their target indefinitely unless the target is too far away; however they can be pacified by planting Pine Cones. Planting one within 16 units away has a 15% chance to pacify them, while within 5 units away has a 33% chance. Planting pine cones ahead of time does not prevent Treeguards from spawning. Attempting to chop down a tree in the presence of a pacified Treeguard will enrage it and cause it to attack.Treeguards will not come from dead Evergreens, Spiky Trees, or Burned Trees.

Hunting
Treeguards have a great deal of health but are slow. Killing the monster by dodging its attack and then running in to strike 3-4 times before dodging again is an effective way to wear it down, although this will drain considerable Sanity. Alternatively, they can be put to sleep using the Pan Flute or Sleep Darts, or frozen with the Ice Staff. Freezing via ice staff is ideal because he will be frozen forever unless he catches on fire. Tooth Traps are useful against Treeguards as they will not only damage them but often get the monster stuck on them.

Leading a Treeguard to other hostile creatures or vice versa is another effective way to kill it. Pigs will attack them on sight, and multiple Pigs can easily disorient a Treeguard by hit & run tactics. They can also be tricked into fighting Deerclopses, Hounds, Tentacles. Another possible way to kill a Treeguard is to pacify it by planting pine cones and light surrounding things on fire, it will catch fire but won't wake up (this method causes the Living logs to burn into ashes).

Having trouble while trying to summon a treeguard is quite normal. A way to speed up this process is to have some pigs with you while chopping down a tree, the pigs will automatically start punching down other trees and will continue for a while even if the player stops chopping. Notice that this way the treeguard will attack the pig and not the player.

Bugs

 * If you attempt to use Straw Roll to sleep while in combat with a nearby Treeguard, the game will not pick it up as being "too dangerous", and you will awake the next day with the Treeguard directly on top of you, still attacking, so take caution.
 * Freezing a treeguard, then hitting it with an axe, spear, pickaxe or tentacle spike (other weapons & tools to be tested) does not thaw the treeguard.
 * It seems that, as of the Strange New Powers update, when a big Treeguard is summoned and you exit the game after a short while, sometimes it will become a medium-sized Treeguard and stay as that. It is unknown if Health and Attack power values are left the same as a big Treeguard.

Trivia

 * Tall Treeguards have the highest amount of health of all the mobs, and deal the most damage to other mobs (not to the player).
 * In the game files, the Treeguard is also named "Leif", which is a male given name of Scandinavian origin. It is derived from the Old Norse name Leifr (nominative case), meaning "heir" or "descendant".
 * Sometimes, after being chased for a while, the Treeguard will walk around randomly, not attacking the player. If this happens, one may use this time to get ready to fight it again, because it will begin attacking the next morning (even if it went passive right after morning).
 * If a Treeguard is being attacked by a hostile mob, it will attack that mob and stop being aggressive to the first mob.
 * If the player dies and respawns, the Treeguard will be pacified.
 * Spiders will not attack a Treeguard if it steps on the web outside their nest.
 * Treeguards may have been inspired by the Ents in J.R.R. Tolkien's "The Lord of the Rings" series.
 * Treguards are most likely Treants for they protect there home land the forest and look identical to them.