The Great Trango is is one of the rare special weapons added to the Zodiac versions of Final Fantasy XII. It is the strongest one-handed sword with the lowest charge time, and second-greatest combo rate (behind the Kumbha, the one-handed katana; katana having higher combo rates than one-handed swords in general).
The treasure in Subterra has 2% chance to spawn. When it does, it has an 80% chance to be 3 gil and a 20% chance to be an item. If it is an item, it has a 95% chance of being a Knot of Rust, and 5% chance of being the Great Trango with the Diamond Armlet equipped.
There are ways to make the treasure always be Great Trango by exploiting the game's random number generator (RNG) in The Zodiac Age version, such as in this YouTube guide. The player should create a new save file in Nalbina Fortress at the beginning of the game as Reks, and then load their main save file. In their main save file, the party should enter Abyssal - South in Subterra, defeat all enemies in that room and claim the Megalixir chest there. The player should leave and re-enter (with a single party member, with weapon and any gear adding status effects removed and the Diamond Armlet equipped), close the application, and then re-open it.
The player should load up their newly created save file at the beginning of the game in Nalbina Fortress as Reks, hit themselves once, then heal until the heal is 94, 86, then 91 in that order. The player should quit to title screen, load the auto-save made in Subterra/Abyssal - South, and the Great Trango chest has spawned to the left. The player should hit themselves twice, heal with Cura five times, have the Diamond Armlet equipped, and open the chest that will have the Great Trango.
Another simpler method to manipulating the RNG to obtain the Great Trango is to create a new save with Reks at the Save Crystal (after defeating the soldiers). After killing every enemy in Abyssal - South in Subterra, removing all but one party member (equipped with nothing but the Diamond Armlet), one must close the application and return to the Reks save previously made, use Cure on him until the number sequence 97, 88 and 86 appear. Without closing the application, one must return to the quicksave made in the Pharos, hit oneself once and use Cure once, then open the chest.
To get Great Trango from Zodiark, the following strategy can be used in The Zodiac Age version: The player can clear Special Charter Shaft off all enemies, leave, and then return. If there are still enemies around, the player should again kill them and leave and return. The goal is to create an auto-save at the start of Special Charter Shaft to a state where Special Charter Shaft has no enemies. The player can then run to Zodiark's lair unopposed, steal, and if they don't get the Great Trango, start again from the auto-save.
Great Trango is a mountain peak in Trango Towers, a family of rock towers in Gilgit-Baltistan, in the north of Pakistan. When the team first started making the International version, the game's director Hiroyuki Itō was interested in mountains and wanted to use interesting names for the game.