Crux

Crux,"The Southern Cross", is a Celestial Spirit owned by Lucy Heartfilia. It is unknown if Crux can be used for combat purposes. However, it is known that Crux has the ability to search for information about Celestial Spirits and their owners by sleeping. His nickname is Crumudgeon.

Loke arc
Crux is summoned by Lucy to see if Loke had any history with a Celestial mage before. During his meditation, he found out that Loke once knew Karen Lilica but he didn't divulge that Loke was really Leo. In the anime, he reappear again with Lucy and her other Celestial spirits in front of the Celestial Spirit King.

Magic & Abilities
Scanning: Crux can scan past people who have been in contact with Celestial Spirits and Celestial mages by sleeping.