History
Alt was a member of the Mitans who lived on the micro-world of Mita. It was a world terrorized by the tyrant known as Togaro. Their rulers had sent their princess to Earth as a child to protect her from Togaro, where she was adopted by an Earth family and named Dianna. When Dianna was an adult, Alt took his fellow Mitan Ailma to the surface world to seek help in defeating Togaro. This led to Captain America and Bucky championing their cause and Alt helped lead them back to his size-changing ship[1].
He piloted them back to Mita where Alt was one of the many Mitans seeking refuge to Earth when Togaro activated a device that was pushing their world into its sun. Unfortunately, the escape ship ended up crashing and Alt, along with the majority of Mitans, were killed in the explosion[2].Paraphernalia
Transportation
Alt piloted a size changing ship that also effected the size of its passengers in proportion of however much it shrank or grew in size. It did not appear to be able to pass through molecules while shrinking or growing.
Trivia
The Latin 'altus' means 'high' or 'deep'.