To acquire an Ararat Artifact, you must defeat the Shadowlord (Astaroth, Faulinei or Nosfentor), who appears inside the hold of the sunken Ararat upon opening the cargo hatch.

Artifacts

Abhorrence

Captain Johne's Blade

Craven

Equivocation

Pincer

Notes

Note that the list above is based on the reports from the players and maybe incomplete. Move your mouse on the images to see the artifact's name or click on it to go to the respective page.
There are also Ararat Stealables (see there).