Young Xehanort

Young Xehanort is the main antagonist of Kingdom Hearts 3D: Dream Drop Distance. He was introduced as an optional boss in the North American, PAL, and Final Mix versions of Kingdom Hearts Birth by Sleep, and he reappears throughout Kingdom Hearts 3D: Dream Drop Distance as an obstacle to Sora and Riku's Mark of Mastery exam.

Kingdom Hearts Birth by Sleep
After defeating the Vanitas Remnant, Terra, Ventus, and Aqua each separately return to the now-ruined Land of Departure, where they encounter Xehanort, his face hidden by his hood. Xehanort draws his weapons and attacks, but after an intense battle, he walks away and disappears.

Kingdom Hearts 3D: Dream Drop Distance
In the Jump Festa 2012 trailer, Xehanort encounters Sora and Riku in La Cité des Cloches and Traverse Town respectively. In the former, he is accompanied by Vanitas.

In the February 2012 special trailer, Xehanort appears before Sora and Riku across various worlds, and Sora and Riku prepare to fight each time they encounter him. Unlike Riku and Sora, his attire doesn't change when he visits The Grid. At one point in La Cité des Cloches, he is accompanied by Ansem, Seeker of Darkness, and in the World That Never Was, by numerous hooded figures.

Appearance
Young Xehanort, true to his name, resembles Master Xehanort in his youth, and wears a Black Coat. When he first appears in Kingdom Hearts Birth by Sleep, he wears the hood up. He wields two weapons that bear a striking resemblance to Xemnas's Ethereal Blades, but appear to have hilts, which many of Xemnas's blades do not. The blades are made of light blue energy and the black handles are somewhat reminiscent of the Terminus and Ruination Ethereal Blades. The blades can be combined into a dual-blade, and extend to be lashed out like a whip. Xehanort wields these weapons with a reverse grip, similar to the unorthodox way Ven wields his Keyblade. In Kingdom Hearts 3D: Dream Drop Distance, Xehanort wields these weapons again, along with a slightly changed No Name Keyblade.

In Kingdom Hearts Birth by Sleep, Xehanort's body model is a copy of Saïx's, though it is unknown whether this has any deeper meaning.