Many years ago, a group of Skylanders known as the Trap Team fought and defeated villains- the Doom Raiders. After that, these villains were locked up in Cloudcracker Prison, a jail made out of the legendary substance Traptanium. However, Lord Kaos has exploded the prison, blasting the Trap Team far away from Skylands, and they began to shrink. At the same time. the Traptanium begins to transform into Elemental Traps, which you must use in order to trap the Doom Raiders and other villains in after defeating them.
—jtalford-83404