Treeguard

Treeguards are Monsters that can occasionally transform from Evergreens when a nearby Evergreen is chopped down, and they are initially hostile towards the wood-cutter. They have very high health and damage and are capable of killing an unarmored character in three strikes. Treeguards do not spawn until 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, and after Day 80 up to 3, given there are enough Evergreens nearby. They can spawn from any size Evergreen tree, besides an Evergreen sapling (from a recently planted Pine Cone). A Treeguard takes four blasts from the Ice Staff to be frozen. When killed they drop Monster Meat and 6 Living Logs.

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 determines 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. Treeguards will not come from dead Evergreens, Spiky Trees, or Burned Trees.

Hunting
Treeguards have a great deal of health but move slowly. Killing the monster by dodging its attack and then running in to strike multiple times before dodging again is an effective way to wear it down. Alternatively, they can be put to sleep using the Pan Flute or Sleep Darts, or frozen with the Ice Staff. 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 Spider Queens and Tentacles. Another possible way to kill a Treeguard is to pacify 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).

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.
 * As of the The End of the Beginning update, there seem to be a bug related to Treeguards spawning. Some users report that on different than default Treeguards spawn rate world customization setting the effect of the setting seems to be inverted.
 * More than 1 Treeguard has been reported before day 10.

Trivia

 * 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, 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 switch aggro towards that mob.
 * If you die and respawn with an Amulet or a Touch Stone, the treeguard will be pacified.
 * As Treeguards will follow you regardless of obstacles, you can repeatedly lure it through a lit campfire to cause damage and eventually kill the creature (keep in mind that this is a long and tedious process (it takes 12 damage/second while burning), and that it will disintegrate most of the Treeguard's loot, it is recommended to use this technique to weaken the creature, before dispatching it with a weapon). One may even attempt to pacify a Treeguard over a burning campfire.
 * It takes 40 hits with a tentacle spike to kill a medium sized Treeguard with Wilson.
 * Even though it only takes one unfelled tree to spawn a treeguard, they appear to have two tree stumps as feet. It is unknown where the other one, or the other limbs for that matter, come from.
 * Considering the extreme damage that treeguards can do to a player, it is greatly probable that their "fingers" (made up of what appear to be pine needles) are razor-sharp, or at least effective bludgeoning weapons, as is probably the case with lumpy treeguards. (see below)
 * Treeguards spawning from lumpy evergreens appear to be rather sad, due to their frowns. This is extremely likely a refference to Wilson's quote when examining lumpy evergreens: "this sad tree has no cones"