Name: Sirius (the Myrmidon Ranger)
Age: Unknown (probably around 3000 years or older)
Appearance:

Olympus Medallion/Power Ranger Color: Achilles Ring/Bronze (not exactly a medallion but the sixth ranger always has a unique morphing style)
Weapon: Achilles
Shield and
SpearZord: Bull (which first appears feral but transform into a Minotaur Megazord)
Bio
Long ago, after the Trojan War, and the death of Achilles, Sirius was a very skilled Myrmidon. So skilled, the Gods chose him for a task they deemed very important. He was charged with protecting the Olympus Urn (a jar that seemed to serve as a gate between two worlds) and was given the Achilles Ring so that the might of Achilles could be called upon in time of need. Around 3000 years passed, and Sirius grew weary of the task and desired his mortal life to be returned to him. When the Urn shattered, Sirius was finally released. But, in order to keep his newfound freedom, he must prevent the Rangers from gathering the shattered Urn (which would mean serving the very being he was supposed to be protecting the world from).
Pot Luck: An ancient guardian like Sirius has no real hobbies. Sirius is still getting used to the modern world and its ways. In fact, he doesn't even fluently speak English yet (he still speaks heavily in ancient Greek). Secondly, Sirius prays to gods that are considered myths, often times asking for a quick blessing from Ares before entering battle.
(I hope I got the bio stuff right...)