Aren was the name of an elven ring, embedded with a sapphire specially cut for the purpose of holding large amounts of energy. The first known holder was the Rider Brom. It had the yawë inscribed on it, signifying that the wearer was an Elf-friend. It became one of Eragon's possessions after Brom's death.
According to Queen Islanzadí, Eragon should not have worn it, as it was not gifted to him directly. However, due to Eragon saving Arya and all that he had done, the Queen bestowed the ring upon him and named him an Elf-friend.
In Brisingr it was revealed that, during Brom's self-imposed exile in Carvahall, he stored away every bit of energy he could spare into the sapphire jewel. It also stated that after Eragon washed away all of his aches and pains, he found that he had taken very little power from the ring, showing the huge extent of the power that had been stored in the ring.
In Inheritance Eragon finally used Aren's stored energy to throw rubble and debris up towards Thorn and Murtagh during the siege of Dras-Leona. It is said the amount of dirt would take 50 men several days to move.
- Aren's sapphire was initially speculated to be Saphira I's Eldunarí. However, Christopher Paolini disproved this in an interview, clarifying that Aren had been made by the elves and that it was expertly crafted to hold extreme amounts of energy.
- Aren may be a word edited from 'arene', a type of hydrocarbon which has at least an aromatic ring. In chemistry, an aromatic ring looks like a ring, so this may be the reason why Aren is a ring.