Terra's adventure in the Land of Departure is the same as that of Ventus and Aqua's. The only main difference between their starting battles is how they are played out. The Cutscene sections (Highlighted in Italics) contain massive spoilers. Read at your own risk.
Cutscene: Mark of Mastery Exam, Part One
The story begins after the Tutorial, where Aqua and Terra stand before Master Eraqus, who intends for the two to perform their Mark of Mastery Exam, while Ventus watches them from the sidelines. Eraqus summons orbs of Light for Terra and Aqua to vanquish, but Master Xehanort, who is watching the test unfold alongside Eraqus, secretly adds Darkness to them, making them inherently dangerous. Ventus ends up assisting Terra and Aqua, who are now in actual danger.
Boss Battle: Orbs
(Rewards: Maximum HP Increased! Learned Style: Critical Impact)
This battle serves as the player's test of applying all they have learned up until now. The Orbs are fast, but don't hit very hard. Ventus and Aqua will do the majority of the fighting, so instead of going after their targets, have Terra attack any Orbs that cross his path. His attacks are powerful but slow, so don't expect a full three-hit combo to connect, since the Orbs will dash away at warp speed if in danger. The Orbs can attack from all sides, but the damage they do is mediocre, so unless the player does absoultely nothing, they should win with ease. Terra receives his signature Command Style after this battle, where the Command Style mechanic is introduced and explained.
Cutscene: Mark of Mastery Exam, Part Two
After the Test, Eraqus remarks that though the test wasn't what he had expected it to be, he decided to let it happen. For the next portion of their test, Terra and Aqua are to face each other in combat. During their battle, A brief power of Darkness envelops Terra's hand, though he manages to supress it. After the fight, Eraqus decides that only Aqua has reached the Rank of Master, since the display of Darkness Terra has shown has proved that his Heart is not yet ready. Keeping his composure, Terra excuses himself from the room, while Eraqus proceeds to talek to Aqua in private. (The conversation isn't heard)
Cutscene: Darkness Within
Terra sits on the steps of the Land of Departure's Forecourt entrance, brooding over the show of Darkness he had expressed. Master Xehanort comes to comfort Terra, explaining that Darkness shouldn't be supressed, but channeled. Terra tries to ask more, but the Land's warning Bell rings, prompting Terra to return to Master Eraqus.
Cutscene: The Unversed
Terra and Aqua are seen listening to Master Eraqus, who explains that a close friend and former Keyblade Master, the wizard Yen Sid, has told him of a new threat that has been eveloping the worlds. Monsters of negative emotion that Yen Sid has dubbed "The Unversed" are spreading across the Worlds. Eraqus opens the gate to the Lanes Between, charging Terra and Aqua to destroy the Unversed and find Master Xehanort, who as oddly disappeared.
Cutscene: Departure
Terra runs to the center of the Forecourt as Ventus runs out to meet him. Ventus tries to say something, but Terra joingly rubs the boy's hair, saying "It's alright." Terra then taps the armor piece on his shoulder, as he throws his Keyblade into the air, it transforming into his Keyblade Glider, while the boy's body is now enveloped by his Keyblade Armor. Terra hops onto his Glider and leaves without delay, marking the true beginning of the game.
Upon Revisit
After completeing Terra's first world, the "Enchanted Dominion," the player can return to The Land of Departure to claim four treasure chests. Events in the story may cause the Land to be unaccessible for a time, so it is highly recommended that the player claim the chests immediately after completing the Enchanted Dominion, to avoid hassle.