From Halopedia, the Halo wiki
Tantalus (named for a figure from Greek mythology) is a human Inner Colony of the Unified Earth Government, located in the Epsilon Eridani system. The colony had a small contingent of UNSC Navy warships orbiting the world.
During the Fall of Reach in 2552, these ships were called upon by Admiral Roland Freemont to aid in the defense of Reach. Like all other human colonies in the Epsilon Eridani system, Tantalus was attacked during the Covenant's invasion of the system, though the colony's fate remains unknown.
In the 2001 version of Halo: The Fall of Reach, Admiral Roland Freemont requests all UNSC ships from the Epsilon Eridani, Tantalus, and Jericho systems to aid in the defense of Reach. However, the 2011 Definitive Edition removes the latter references, likely because the so-called "Jericho system" had been compromised in 2535, while the Halo Encyclopedia had previously established Tantalus to be a planet in the same system as Reach.
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