Harpies

Jason Avery is an ex-cop now working as a museum security guard. Armed thieves break in intent on stealing a priceless obelisk that looks like a glowing crystal dinosaur egg that's stored within this vault-like stone structure that looks like someone merged a Tardis with the Stargate. The scientist/anthropologist/whatever behind the theft talks of the obelisk giving him the power to control harpies, demonic winged female monsters of classic mythology. Through a series of contrived events, the obelisk opens a time portal that Jason promptly falls into, crash landing over a thousand years in the past in a land threatened by evil harpies.