The Shrieker

"Deep within the heart of the Weald stands a gigantic tree that towers above all other trees, and hidden within the gnarled and twisted branches of this tree is the Shrieker's Nest. Like the Noble Raven depicted on our family’s Coat of Arms, this poor creature has seen better days, for the corruption that plagues the estate has twisted this feathered bird into a feathered fiend. Despite being corrupted, this feathered fiend is still a Raven at heart and has an eye for everything that glitters and shines. The Nest of the Shrieker is decorated with all the shiny and glittering Trinkets it has stolen from our Trinkets Chest or taken from the dead bodies of our fallen heroes. Reclaiming these items will not be easy, for the Shrieker will defend its Nest from any intruders. But if Shrieker feels that it is not worth its life to protect his hoard of treasures, it will abandon its nest and escape to live another day, free to steal more of our rare and valuable Trinkets."

Behaviour
The Shrieker is a Eldritch/Beast Event Boss found in the Weald fought alongside its Nest, both of which take up two slots. The Shrieker has attacks that move it forward and backwards, meaning you're going to need to switch between attacking the front and back lines.

On the Shrieker's last turn during Round 4, it will use Shrieking Flight, dealing 50 stress damage to all heroes before flying away, ending the battle.

Strategies
The fight starts as soon as you enter the zone, making buying Items used outside of battle, such as food, shovels, and keys useless. As the Shrieker afflicts your heroes with Bleed and Debuffs, buying Bandages and Herbs to cure them is recommended, as is buying Holy Water as it can be used in battle. Also, radiant light bonuses (such as sun rings or Quirks like Photomania) are worthwhile, as your torch won't go down at all unless you douse it yourself.

It is recommended to ignore the Shrieker and instead focus on destroying its nest, unless you want its unique positive quirks. The Shrieker drops no loot upon dying, but the nest will drop up to 5 Puzzling Trapezohedrons (1 at apprentice difficulty, 1-3 at veteran difficulty, and 3-5 at champion difficulty), worth 3500 gold each. If you have the mission from the "A Thief in the Night" town event, you will recover your lost trinkets regardless of whether you kill the Shrieker or not.

The nest is immune to damage over time effects and debuffs, so you should focus on pure damage attacks.

The Shrieker has very high dodge, making it incredibly hard to hit. Even with accuracy boosts from trinkets or the Jester, you'll likely only have between 40-60% chances of hitting it.

With the exception of Peck and CRITS, the Shrieker's attacks only deal 2 damage. Because of this, buffing PROT isn't very helpful, and it would be better to buff DODGE instead. His main damaging move, Peck, deals 6-10, 8-13, or 13-19 point of damage depending on the version of the boss. Peck also has a high bleed chance.

Bringing the Man at Arms is a viable strategy, both giving your team high dodge, and being able to buff your own team's accuracy.

The Occultist in 3rd is very valuable for 2 reasons: it lowers the enemy dodge with his move Vulnerability Hex, and he does bonus damage to the Shrieker with his Sacrificial Stab (+15% DMG vs. Eldritch).

The Arbalest in 4th position is also a viable pick. The reason is three-fold: 1. Mark Target will reduce dodge and increase damage, which is crucial for dealing with both Shrieker and Nest. 2. Snipe is an ability that will allow you to hit either target at any time (since the Shrieker and Nest both take up 2 positions in the fight), it has a high accuracy rate and good damage (added upon by Mark Target). 3. Arbalest bandages, while not a strong heal, will prevent the loss of heroes at Death's Door when in a pinch (focusing on dodge should help prevent this) from the several pecks you will receive during the fight.

One viable party composition with 3-4 Sun Ring or other +ACC trinkets for Stygian Horrid Shrieker if you intend to kill it is:

Hound Master / Hound Master (or Highwayman) / Man-at-Arms / Flagellant (or Leper)

With Dog Treats and holy water, Hound Master uses Hound's Rush from the very beginning while Man-at-Arms uses Command to boost accuracy and then Retribution. In this way, Horrid Shrieker can be killed within 4 turns.

Shrieker Trinkets
Sometimes the event Shrieker's Prize will be showing. This will allow the player to hunt down The Shrieker for a chance to aquire a Shrieker Trinket.

Corvid's Quirks
Heroes who survive the battle with The Shrieker may contract one of several new quirks. Successfully killing The Shrieker increases the chance to get a positive quirk instead of a negative quirk, but all quirks are possible to contract regardless of the outcome of the fight. The following list is of the discovered quirks and their effects:

Abilities
Apprentice =

Veteran =

Champion =

* Only used as its last action during round 4. Also cannot be riposted, so isn't a last chance to get the kill.

Trivia

 * While the battle itself remains unchanged for the quest you fight it in, the music for the battle does not. If the quest is Shrieker's Prize, it is the Mournweald Encounter, the normal battle music for the Weald. If the quest is A Thief in the Night or recovering lost trinkets from fallen heroes, the music is Town in Chaos, the battle music from Wolves at the Door.
 * When The Shrieker "flees" the quest condition about killing 1 Shrieker is fulfilled; the Shrieker may in reality be killing himself by using Shrieking Flight.
 * There are Apprentice and Veteran version of this boss. They are called Callous Shrieker and Cretinous Shrieker, respectively. While Shrieker's Prize will always feature the Champion Version of the Boss, A Thief in the Night may feature the Apprentice or Veteran version of the boss, depending on the highest rarity of Trinket that was lost on the battlefield.
 * This is the only encounter in the game that appears in the first room. The player can still camp in the first room in other expeditions after exploring a minimum of one room and coming back, then getting ambushed in the night.
 * The name Corvid comes from Corvidae, which wikipedia defines as the "cosmopolitan family of oscine passerine birds that contains the crows, ravens, rooks, jackdaws, jays, magpies, treepies, choughs, and nutcrackers."
 * The Shrieker's attacks are programmed to move him forward and back 4 positions. This is despite only requiring to move 3 positions to always end up in the first and fourth positions after executing each move respectively.