When Set, Buckle increases its Adept's base HP by 11, base Defense by 2, base Agility by 3, and base Luck by 2.
When Buckle is unleashed in battle, all currently active and alive Adepts get buffed with a 25% temporary increase to their respective defense ratings. This is twice as strong as Protect/Protector. All defense-boosting effects come in the form of 12.5% "stages", so therefore Buckle boosts each Adept's defense rating by two stages, and the maximum amount of stages an Adept's defense can be boosted to is four, at +50%.
In Dark Dawn, Buckle's unleash animation visually resembles the user summoning the 3D model of Buckle, which hovers around briefly as each Adept has sixteen tiny gray squares arrange to form a four-by-four tiled square in front of him/her in order. A moment later, each Adept has a small yellow circular field climb up through their legs to indicate a statistical boost.
Golden Sun: Dark Dawn: Buckle is automatically acquired in a cutscene late in the game. In the palace in Yamata City, when you approach the sleeping Himi while the Third Eye item from Warrior's Hill is in your inventory, story-relevant cutscenes transpire that result in Himi permanently joining your party. She brings with her this Djinni along with five other Djinn - Geode, Clover, Magnet, Pepper, and Swift.
General: The mass-defense-boosting effect that Buckle and other identical Djinn provide is a highly effective buffing effect in any of the games because many enemies' attacks are physically based and will be lowered a large amount, justifying the turn an Adept takes to cast it. However, the additional defense works bests against enemies without many offensive Psynergy or monster skills that are based on elemental power rather than elemental physical attacks.
Golden Sun: Dark Dawn: Buckle is a valuable battle effect because it is 2 stacks of the Protect Psynergy in one maneuver, causing what physical attacks enemies have to be critically lowered. This is not to mention that the Djinni is put on Standby after this, so it can perform a Venus-aligned Summon in a subsequent turn. Buckle is, however, critically undermined for two reasons: it has much less opportunity to prove itself useful than its identical counterpart, the Venus Djinni Brick, which is found much earlier in the game. Buckle therefore counts as a late-game copy to Brick that the party may decide to additionally use. The other reason Buckle and similar Djinn are not as useful in practice as in concept is how enemies generally do not inflict as much damage and are defeated more easily than in previous games. Some sort of self-imposed challenge would have to be in place in order for the enhanced defense to be about as useful as upgrading the party's attacking statistics.
Buckles are clasps, usually made of metal, used to secure loose ends of an object in place. Titan could either refer to the Titans, a race of Greek deities descended from Gaia and Uranus, or titanium, a very lightweight and durable metal.