Captain Grimm

Captain Grimm is a Skeleton Lord boss in Sea of Thieves. He is one of the four Ashen Lords to serve under Captain Flameheart. He can be encountered and battled during the Ashen Winds World Event. When defeated, Captain Grimm drops an Ashen Winds Skull and around 15 Devil’s Roar Treasure items.

Background
Very little is known of Flameheart and his Ashen Lords. According to Duke, Captain Grimm was responsible for constructing the Fortresses and Flameheart's Lairs to defend and hold all the Treasure that they stole. Judging by his dialogue during the fight, Grimm himself has a rather playful personality.

In the Sea of Thieves Origins #1: Champion of Souls comic, Sir Arthur Pendragon is revealed to have battled (and defeated) Captain Grimm in the past during an attack by Captain Flameheart's armies on an unnamed outpost.

Locations
Captain Grimm only makes an appearance during the Ashen Winds World Event, where he can be one of the four encountered Lords. The Ashen Winds World Event is signified by a red fiery Tornado in the skies and can appear at the following locations:
 * Kraken's Fall - Center of the island, between the two bays. There is an Ammo Chest by a pond nearby.
 * Shipwreck Bay - Next to the inner bay. There are two Ammo Chests nearby: one south of the bay by a large rock and one close to Grogsoaked Ed in a fenced area.
 * Marauder’s Arch - In the eastern fortified area. An Ammo Chest can be found inside the fort itself.
 * Cannon Cove - On the beach area of the cove. There is an Ammo Chest in the beach Camp.
 * Wanderers Refuge - On the beach south of the northern cave. There is an Ammo Chest on the Western shore of the Island.
 * Mermaid's Hideaway - Next to the inner pond area. There is an Ammo Chest by some Barrels under the Northern arch.
 * Devil's Ridge - Next to Martha the Fierce by the waterfall pond. There is an Ammo Chest close to Martha.

Attacks
Captain Grimm has the same moveset as all Ashen Lords with the major difference being the taunts signalling the attacks.
 * Melee Attack - The most basic out of all the attacks, the Ashen Lords will strike any players who get too close to them by causing damage and knocking them back.
 * Fire Breath - The Lord tries to distance nearby players by spewing flames out of their mouth akin to a flamethrower. Any players inside the breath attack take heavy damage. This attack also sets the Lord on fire, dealing fire damage all around them.
 * Lunge Attack - The Lord attempts to close the distance between them and the player by jumping towards them, dealing damage and knocking them back when hit.
 * Boulder Throw - There are two versions of this attack: a small quickly thrown rock or a larger boulder that can reach remarkable distances. The smaller rock throws do not have voice-lines. The larger boulders deal considerable damage and set hit players on fire. It seems that both of these attacks can be cancelled with damage.
 * Summon Skeletons - The Lord summons a handful of Ashen Skeletons to fight for them. The Lord seems to be able to spawn two groups of skeletons. These skeletons are relatively weak and can easily be taken out with a cutlass lunge. The summoned skeletons can spawn with no weapons, a cutlass, blunderbuss or flintlock.
 * Ash Cloud - The Lord will cast a thick and wide cloud of Ash that drastically lowers visibility around the Lord and outside. Everything inside the Ash Cloud will have an auditory echo to it.
 * Shockwave - The Lords gain access to this attack during the second phase. They will gather strength and pound the ground with a fiery blast, setting any nearby players on fire, dealing heavy damage and sending them flying in the air. The closer players are to the Lord, the more damage this attack will deal. Since players are thrown high in the air, they will also receive fall damage unless they have their back to a wall or are in water. Unlike the Skeleton Lord shockwave attack, this attack also damages the masts, capstan and wheel of any nearby ships.
 * Volcanic Eruption - The Lords gain access to this attack during the final phase. They will kneel and summon a volcanic eruption out of the sky, while also using the Fire Breath attack the whole time. Making any close attacks risky. During this attack, like under a Volcanic eruption, all the surrounding water will become superheated, geysers will appear on the Island itself and volcanic Rocks will fly from the skies, often instantly killing any hit players. This attack is also devastating to any nearby ships.