Trinity is a special ability introduced in Kingdom Hearts. The ability is represented by a symbol composed of three hearts connected by a circle.
In Kingdom Hearts, Sora can activate the "Trinity" ability while standing on a Trinity Mark while Donald and Goofy are in the party. This will cause the trio to perform an action respective to the mark's color, which usually results in opening a new path or revealing a rare treasure. The friends learn five different Trinity commands throughout their journey, each with a different color, as well as the combat ability "Trinity Limit". Certain Trinity Marks must be activated to progress through the story, but most are optional and only required for completing Jiminy's Journal. Almost all Trinity Marks can be activated at any point in the game, with the exclusion of a single Red Trinity Mark in Oogie's Manor in the original Kingdom Hearts. In that version of the game, the mark causes a small storage shed to disappear when activated, but the mark disappears once the manor is destroyed in the battle against Oogie Boogie. In Kingdom Hearts Final Mix, this Mark is moved under the arch below the manor, so that it is still accessible after the battle, but it will still cause the shed to disappear when activated.
The first obtained in the game and by far the most common, Trinity Jump (トリニティジャンプ, Toriniti Janpu?) is learned after defeating the Guard Armor boss in Traverse Town. The blue marks represent the ability Trinity Jump; Sora, Donald and Goofy bounce on the floor, shaking treasure loose from somewhere above them, or accessing higher levels. Although this is the first mark to be learned, activating blue Trinities is not required to complete the game.
Second to be discovered, Trinity Charge (トリニティスマッシュ, Toriniti Sumasshu?, lit. "Trinity Smash") is learned after sealing the Keyhole at Deep Jungle. Sora, Donald and Goofy will charge at a wall or barrier and break it, revealing a new path. Trinity Charge is required at some points in the game to progress the story, especially in Traverse Town.
The third Trinity ability, Trinity Ladder (トリニティスタワー, Toriniti Tawā?, lit. "Trinity Tower") is learned after Agrabah is locked. They represent Trinity Ladder, where Sora, Donald, and Goofy climb on top of each other to reach something up high. The green Trinity is required at one point in Neverland; it must also be used to access the Moogle shop above Cid's store in Traverse Town and activate item synthesis.
The fourth Trinity ability to be learned and the rarest of them with only a total of four in the game, Trinity Push (トリニティスショヴ, Toriniti Shovu?, lit. "Trinity Shove") allows Sora, Donald and Goofy push a heavy object around. In order to obtain this mark, Sora must win the Hercules Cup in Olympus Coliseum; he promptly puts it to good use by using it to reveal the Coliseum's Keyhole.
The fifth and final ability that Sora, Donald, and Goofy learn is Trinity Detect (トリニティスディテクト, Torinity Ditekuto?); the trio raise and point their weapons, summoning a Treasure Chest. It is learned after Riku is defeated for the first time in Hollow Bastion. This Trinity is not required to complete the game, but does net some useful things, especially the Lady Luck Keyblade and the Violetta staff for Donald.
The strongest Trinity ability is actually an attack, and is the only Trinity ability to reappear in later games. The technique consists of Sora creating an intricate Trinity mark on the ground and activating it with his Keyblade. It consumes all of the party's MP, but deals enough damage to wipe out any minor enemies within its area of effect, unless they are temporarily invulnerable, like the Shadow, Neoshadow, or Black Fungus. It is learned after completing the Hades Cup.
List of Trinity Marks
Kingdom Hearts Re:Chain of Memories
A Green Trinity symbol represents friend cards at the top left corner of the screen.
Kingdom Hearts II
A White Trinity symbol appears next to "Button" during Trinity Limit.