One of the things I loved doing was working towards certain curses in this game, so I think its a crying shame we don't have more to work towards. So I have a few ideas for some that already exist in a sense.
Glacial Curse - Frosty Pirate curse, similar in name to the curse afflicted by the pets of similar name. Exact same frozen appearance but on our pirates.
Reaper's Heart Curse - Again inspired by pets of a similar name just add effects to the player's bodies that make us look like an animated Reaper's Heart Doll or something.
Winter's Bite (Frostbite) Curse - A slightly frosty cursed (Similar in appearance to the ashen curse but blue, giving a more icey feeling. Also some frosted limbs would go a long way to sell the effect)
Plaguebile (Rotsoul) Curse - Sickly looking curse that has your pirate glowing green eyes with a few pustules and growths on the player's body or just a general sickly looking appearance.
Bloodthirst Curse - Glowing Red eyes pierce the darkness and a crimson smile flashes its fangs. Basically a curse that applies a red glow to eyes (And maybe mouth?)
Mer's Metamorphosis Curse - A curse that applies fish scales to a pirate's form as well as gills along the neck/sides of torso, making you look like a mer-kin.
Medusa's locks Curse - Just adds a few animated snakes to a pirate's head that match hair color.
Savage Beast Curse - Some claws and fur, as well as predatory eyes gleam in the darkness. (Think a bit like a werewolf curse but not a full transformation. Just some fur on the arms/legs with slit irises and claws from the fingertips)
All of these curses can come in multiple variants as well to give an even wider degree of customization. Different colors/tones/hues/variant designs in patterns.
So far the Ashen Curse is the most common because it looks dope as hell, it would be cool to see more earnable curses like the Ashen Curse rise to prominence among the sea of thieves.
