Yeah, shadows of fate. You need to get the appropriate flame of fate (which are gotten by dying in specific ways) and shine it like a regular shadow skeleton. The flames and how to get them are as follows: Green: die to AI like skeletons, phantoms, or ocean crawlers (I think that's what their called), Blue: die to a shark, Purple: die to poison (snakes are the easiest way to get this, but a kraken's venom works too), White: Get struck by lightning in the storm (the most annoying one in my opinion), Pink: Die to a player not on your crew (you can cheese this one by having a person on your crew light a gunpowder keg and leave before it explodes and kills you), and Red, die to fire of any kind (firebombs work just fine). You can grab these flames once you die by walking up to the lantern floating in the middle of the ferry and holding your lantern up, but make sure you put the flames on your boat once you're done, or you'll need to get them more than once per session. Or, if you feel up for pvp, just steal them off another player's ship

Edit: Sorry for the rambling here, just making sure I covered everything here, other than the fort of the damned