On Wednesday night, the trailer to "Avengers: Age of Ultron," the highly anticipated sequel to the 2012 blockbuster, leaked online. There was one element that stood out above everything else - even the dreamlike vision of the entire team - it was Ultron. 

He apparently has a robot army at his command.

And his eerie voice dominates the trailer in voice over.

Ultron really is terrifying. Almost all of the dialogue in the trailer comes from the big bad himself. It’s really hard to overstate how great James Spader’s performance is - he doesn’t sound like a machine. He sounds frighteningly alive as he quotes lines from the classic Pinocchio song "I've Got No Strings."

The first time we see Ultron, he comes stumbling out of Tony Stark’s workshop in Avengers Tower, as a dangerous party crasher.

Unlike the phase one Marvel superheroes, many people don’t know who Ultron is or how he may fit into this upcoming chapter of the story. IGN has put together a good video giving newbies a primer on the character, also giving some insight in how Ultron may be featured in the upcoming Avengers sequel.

Everything you really need to know about Ultron:  He's a crazy robot that wants to eradicate humanity.

He was created by Ant-Man, a character who won't be appearing in "Avengers: Age of Ultron" because he's already scheduled to make his cinematic debut in Edgar Wright's movie, scheduled to be released afterward. In the 40-plus-year history of the character - Ultron made his debut in 1968's Avengers #55.

Somehow, with just seconds of footage, Whedon has established Ultron as an intellectual, terrifying villain, and we can’t wait to see more.