Skeldritch is the sixth boss in Spirit Tracks. Its appearance is very similar to that of Stallord; it appears as a large skull with a spine that rises from the center of a large, ruinous room filled with sand, although it lacks arms and a ribcage, and it also sports a large, horned helmet. The skull is also more human-like than Stallord's beast-like skull.
Skeldritch will fire large rocks at Link, at which point, he will need to use the Sand Wand to create walls of sand that will deflect the attacks. He can then push one of the rocks into a nearby catapult and fire it back to one of Skelditch's vertebrae to destroy it. However, the last three bones are protected by armor, and Link must get Skeldritch to face a different direction in order make his exposed point face a catapult and fire at the switch with an arrow while Skeldritch is in this position. Skeldritch will also shoot a laser from it's mouth to try and strike Link if and whenever possible. When merely the head is left, it will float around the arena, and try to ram into Link. If surrounded by a wall of sand, Skeldritch will attempt to break out, allowing Link to attack the ruby-like weak point on the back of his skull. Alternately, Link can lift himself up using the Sand Wand any time he is behind Skeldritch to reach the boss's weak point.
In the PAL version of Spirit Tracks, Skeldritch is named Capbone. The name most likely derives from the words cap and bone, as the boss sports a helmet (cap) and is skeletal in appearance (bone).
Skeldritch's name is derived from the words "skeleton" and "eldritch". "Eldritch" is a word meaning "unearthly," "alien," "supernatural," "weird," "spooky," or "eerie."
The "hopping head" phase of the battle strongly resembles the last phase of the fight against Eox in Phantom Hourglass, complete with a vulnerable gem-like object on top of the boss's head.