The crystal T-1000

As SKYNET loses the battle between humanity and machines, it sends a T-1000 nicknamed "Darby" to enter a portal to save SKYNET. However this plan backfires and the T-1000 ends up in Beach city and in a brand new timeline, a timeline where SKYNET never existed, he has also gone rogue and has decided to do new orders on his own, protect The crystal Gems.