Shambler

It is said that since the dawn of time Mankind has been born with an instinctive fear of the darkness; a fear of the stalking predators in the night, a fear for the poisonous and bloodsucking horrors that crawling in the deepest dark and a fear for the unknown and unseen things that dwell in the darkest shadows, just out of sight of human eyes. These primordial fears are justified for there is a creature, a predator, that not only haunts the collective nightmares of mankind, but patiently waits until the last glowing embers of light have died and the deep, suffocating darkness claim dominion, before it strikes.

A predatory nightmare summoned from the darkest recesses of the unknown, a star-spawned horror, an infinite malignity of the stars that inhabits the Void between Worlds that was never meant to be seen by mortal men. The Shambler is a truly nightmarish beast that lurk with every shadows, waiting until all forms of light are extinguished so that it is able to enter in our world and hunt its favorite prey and feed its spawn. This monstrous thing is capable of warping the fabric space and time and pulling its prey into the Void between the Worlds. The only way to escape the endless darkness of the abyssal Void is to kill this nightmare and its spawn. The few who have survived an encounter with this nightmarish beast would dismiss the encounter as a fever dream, if not for the corpses of their companions and the twisted pile of tentacles and claws that is the corpse of the Shambler.

Whether or not the Ancestor knew about the existence of the Shambler is up for debate, however considering the amount Shambler’s Altars that can be found scattered across the Estate, it is safe to say that he may had a hand in placing these Altars or at least in bringing them to the Estate.

Behavior
A predatory nightmare summoned from the darkest recesses of the unknown, the Shambler is an Eldritch mini-boss that lurks in blackest pitch, dropping ancestral trinkets when killed. When traveling with your torchlight at 0, the Shambler will rarely appear in any location as a hallway fight (Apprentice level - 1%, Veteran level - 8%, Champion level - 12%) or when a Torch is used on a Shambler's Altar (which instantly reduces light to 0).

Before attempting to fight a Shambler, be warned that this is one of the hardest enemies in the entire game. It is very easy to lose heroes here and the longer the fight lasts, the stronger it becomes. Preparation is needed.

The party will always be surprised when encountering a Shambler. If summoned from an altar, the Shambler will automatically bring the torchlight down to 0 and will prevent the party from lighting torches while fighting it. The light level will also stay at zero if using a hero's ability that would normally increase light levels. If summoned but then run away from, the Shambler will appear again as the next encounter. Don't summon it unless the party is ready to kill it.

Due to a very low speed, it will most likely act last, using its bleed or blight attack and summoning 2 Tentacles. Unlike the Shambler itself, Tentacles have a very high speed; they are very likely to take actions before the party, applying a strong buff to themselves. If one or both of the Tentacles are killed, the Shambler will re-summon them. If both are left alive, the Shambler has a chance to use Stentorious Lament, which will shuffle your party's formation.

Ancestral Trinkets
The main reason for hunting down this monstrous creature is because it carries with it Ancestral Trinkets, items once carried by the Ancestor that contain terrible power. Every time a Shambler is slain it will drop one of the 5 trinkets below. However, since only one of each trinket can exist in the player's inventory, when they are all obtained Shamblers will no longer drop Ancestral Trinkets unless one of the trinkets is lost.

Abilities
Apprentice =

Veteran =

Champion =

* Summoning will occur whether the ability lands or not.

Strategy
The Shambler is very strong, stronger than some bosses. Most of the time, it is wise to pass up the opportunity to fight him. Nevertheless, if you decide to summon him, it's better to do so after you've completed the quest objective, as your party will most likely be in no condition to continue the expedition after the encounter with the Shambler.

When dealing with the Shambler it's important to finish the fight as soon as possible. The general strategy is to kill Tentacles and stun the Shambler to prevent him from re-spawning them. If you don't have enough damage or reliable stun to do that, you may leave 1 Tentacle alive and hope the Shambler uses Stentorious Lament. It will shuffle your party but not summon a Tentacle. A variation of the Marking Party, however, can ignore the Tentacles and finish the Shambler in 2-3 turns. High Bleed and blight resistance is encouraged. Consider bringing/using Holy Water to buff these resistances at the start of battle.

When assembling a party to hunt the Shambler specifically, consider the following classes: Abominations, with their high speed, can kill both Tentacles with Rake before they buff themselves; Crusaders can also take care of Tentacles with Zealous Accusation; Hound Masters can reduce the Shambler's PROT; Plague Doctors and Bounty Hunters can land stuns (but only reliably if they have suitable Trinkets); Occultists deal increased damage vs. Eldritch and have a +20% damage buff camping skill for your heavy hitters. All of them and the Arbalest have a marking synergy. The Jester can function as a utility class, he can move 3 spaces in either direction to combat shuffles, and spamming Battle Ballad can let your team move before the tentacles. Man-at-Arms works well due to the Shambler and its Tentacles having low accuracy and both of his amazing party buff camping skills.

Please note that the champion difficulty Shambler is much stronger than his previous iterations.

Trivia

 * In the early access and the original release the Shambler left a normal Corpse after it was killed instead of a large one, despite it taking up 2 Ranks during a fight.
 * The Shambler features in two Journals that can be found in the game. The first, "Journal of Darius, Highwayman", ends with Darius' party being ambushed and slaughtered by a Shambler. The other one, "The Blackest of Fates", documents the fate of a party whose occultist, "thrice damned Mizir", activated a Shambler Altar and unleashed a Shambler upon everyone.
 * As of the Inhuman Bondage update, the Shambler will physically drag the party into another dimension. The area resembles a violet galaxy and functions the same as Pitch Black.
 * The name "Shambler" likely comes from the "Dimensional Shambler", one of HP Lovecraft's creation. The Dimensional Shambler is a creature that comes from another dimension and attacks its prey by using a form of hypnosis to make the victim believe they've been dragged into another plane of existence. However the appearance of the Shambler does not match the description given of the Dimensional Shamblers, as they are mostly humanoid. Rather the Shambler's appearance closely resembles the description given of the Shoggoth, said to be "vaster than any subway train— a shapeless congeries of protoplasmic bubbles, faintly self-luminous, and with myriads of temporary eyes forming and un-forming. "
 * Another reference to Lovecraft is when the narrator calls it a "Star-Spawned horror." In Lovecraft's work the Star Spawn are another name for the Cthulhi, which are spawn of the Great Old One Cthulhu, one of the central beings of Lovecraft's mythos.