"Hijack Dragon" (ハイジャックドラゴン Haijakkudoragon) is an attribute. It is currently in Darkness Dragon World and Lost World.
The Hijack Dragons of Darkness Dragon World have an ability simply known as "Hijack". When this ability is used, they choose a monster on the opponent's field meeting certain conditions, and place themselves in the soul. This can result in a variety of things, from simple stat loss to force attacks on the card owner. Some of the strongest Hijack Dragons have abilities that prevent calling over the card, or soul drop/destruction. In Lost World, they still retain "Hijack" except this time the effects are much more devastating, preventing Spells or reducing the Size Limit.