The shrieker itself has 5 attacks, with one of them being a devastating gimmick. There's also a Shrieker Nest on the field, but it does absolutely nothing so don't worry about it.

Because of this, Marks and Debuffs are wholly worthless since they burn out super quickly, to the point where stacking them is practically impossible. The Shrieker itself is a unique and threatening boss: It has high HP values, stupidly high DODGE, and the kicker being that he has three actions per turn. In terms of team-comp, this is one of the few fights where I highly recommend gearing toward the offensive: Hellion/Bounty Hunter/Man at Arms on front for a durable pointman with versatile ranges, Graverobber/Houndmaster for your high speed ranged damage, Occultist/Arbalest for a good back-row offense that can also panic heal, and naturally a Vestal because of course you bring a vestal. Pack items such as medicinal herbs, holy water and band-aids to make the fight much easier. One major thing to note though: The mission itself leads right into the fight, so packing things such as Food, torches, shovels and keys are generally worthless. Since the Shrieker itself is a mission you deploy for, there's an opportunity to prepare for the fight. Either way, the Shrieker tends to throw a wrench into your plans as it swoops in to ruin your day. The big thing to note about this fight is that you do not get to choose when to fight it fighting the Shrieker is entirely based on town events, one of them involving it stealing 8 trinkets lying in your storage, and the other one an active hunt in order to get a unique accessory. The Shrieker is a strange and unique fight in Darkest Dungeon compared to everything else in the game.

Part 20: Miniboss Guide: The Shrieker The Shrieker

Shriekers prize darkest dungeon