Reaper’s Mark

The Reaper's Mark is a symbol in the shape of a Skull, used in numerous places in the Sea of Thieves.

Background
The Reaper's Mark was mentioned in the Athena's Fortune novel written by Chris Allcock. In the novel, the Pirate Lord received a necklace with a "Reaper's Mark" on it as a parting gift from his long-time crewmate Mercia. The necklace was hinted to contain the magic behind the Pirate Lord's ability to live on as a Ghost beyond death. Presumably this effect could be bestowed upon any Pirates that received his favour as Pirate Legends.

Athena's Fortune
Although the appearance or shape of the Reaper's Mark was never remarked upon in the novel, the video game has decided to show it in the Shape of a Skull. The Pirate Lord's necklace and the insignia of the Athena's Fortune Trading Company appears to be that of the Reaper's Mark, depicted in the ghostly green tones of the Pirate Legends in the Athena's Fortune Hideout. The Reaper's Mark also seems to be the logo of the Sea of Thieves video game itself.

The Reapers
Outside the Pirate Lord and Athena's Fortune, it seems that the Reaper's Mark seems to have an entirely different effect on any pirates. First of all, any items with the Reaper's Mark will become cursed with an ominous red smoke that will disclose the location of that item to any and all Pirates on the Seas. This is mostly displayed on the Map Table of a Ship. The Reaper's Mark appears to be related to the mysterious Reapers who have set up their own Trading Company the Reaper's Bones at The Reaper's Hideout. The Reapers are a group of vicious Pirates who wish nothing more than to serve the wishes of the Skeleton Lord Captain Flameheart and oppose any and all other Trading Companies. The Reapers value Pirates who are daring enough to risk their lives by taking on the Curse of the Reaper's Mark on their Ships. It seems that the magic behind the curse of the Reaper's Mark is what envelops the base of the Reaper's on the Reaper's Hideout. The Reaper's Mark has also been seen to interact with any Skeleton Glyphs with a red hue.

The Flag of the Reaper's Mark
There first item in-game to bear the Cursed Reaper's Mark was the Flag Of The Reaper’s Mark. This Flag was the only one to have a special effect tied to it. Whenever the Flag is hoisted on the Crow's Nest from the Ship Flag Box, the Ship will appear on the Map Tables of all Ships to see. This makes the Flag a high-risk item, as it will possibly attract the attention of other Crews looking for a fight. The Flag can also be used to intimidate other Crews, showing that the Ship's Crew does not shy away from attention.

Reaper's Chests and Reaper's Bounties
There are two Chests in-game that bear the Reaper's Mark: The Reaper's Chest and the Reaper's Bounty. These two Chests mainly appear in sunken Shipwrecks and are cursed to display their location at all times on the Map Tables of any Ship. Untouched, these two Chests shoot out light pillars into the sky - green and red for the Reaper's Chest and golden yellow for the Bounty. When picked up, the light pillars will disappear, but the location of the chests will still be visible on the Map. These chests can also be acquired from a finished Fort of the Damned Vault and dug up from Skeleton's Orders Quests. These Chests are only valuable to the Reaper's Bones Trading Company, who seem to open these chests to uncover Skeletal remains for mysterious rituals.

Reaper's Bones Emissaries
Any Crews that wish to Represent the Reaper's Bones Trading Company as Emissaries will be cursed with a Reaper's Mark. Their Ship and its Emissary Grade will be visible for all Crews on the Map Table. Once Reaper's Bones Emissaries reach Grade V Reputation, they will be rewarded with the power of the Reapers, which shows the shadowy locations of ALL other Emissary Ships on their Ship's Map Table.

Trivia

 * The game's logo bears the Reaper's Mark, commonly used as a flat, silhouetted design, often decorated for Content Updates or for various promotions and occasions
 * A painted version of the game's logo also exists and is used in various Sea of Thieves products and merchandise. This painting is titled "Ambush at Skull Cove" adds further details, such as additional pirates, ships, and creatures into the superimposed scene.