This is possibly one of the coolest rare spawns on the Timeless Isle. As I mentioned before, a few need some sort of event or interaction before they appear and this is no exception. First you need to kill Evermaw, the rare elite whale shark that swims around the entire Isle and loot the Mist-Filled Spirit Lantern.
Then head to the Misty Strand and use the lantern at the Cursed Gravestone. This will summon the Dread Ship Vazuvius. Note the lantern is conjured so only lasts an hour which is probably why you don’t always see the gravestone. I suspect the shrine is only active as long as Evermore is alive and probably up to an hour afterwards unless someone summons the ship within that timeframe.
Once the ship is destroyed, you can loot the spoils which includes 1000x Timeless Coins and the Rime of the Time-Lost Mariner – another transformation item.
The buff lasts 15mins while the item has a 2hr CD and no limitation on where you can use it.
Edit: In the latest PTR build, the item no longer affects your mounts.
Plus, the ship now has a knockback so don’t stand too close if you’re melee.