Ground

Location
Ground is located at the top end of Kalay Docks, and is visible to players entering Kalay Port for the first time - it cannot be gotten until later in the game, though. It can only be reached once you've sailed across the Karagol Sea and made it to the other side in Gondowan. Then, by going east from the entrance to Altmiller Cave and traveling the stretch of land bordering the top of the Karagol Sea, reenter Kalay Docks from the top end, and you will be right next to the Djinni, waiting to be collected.

Description
When Set, it increases base HP by 9, base PP by 3, and base Agility by 3.

When Ground's battle effect is used, the user summons an array of energy spheres that slowly gather into the target's position, causing the target to be "unable to move" for one of its actions this turn (meaning the enemy cannot attack at all this turn if it can only act once per turn, whereas a boss that can act twice a turn can only act once a turn). This acts first in battle regardless of the Agility ratings of the user and the target, and it shares its priority with other "acts first" moves like the opponent's Granite and Flash Djinn in VS mode (meaning that the Adept with the higher Agility will use his acts-first move first). It is identical to the TLA Djinni Petra.

Ability analysis
In Golden Sun, Ground is the only effect that prevents an enemy's action entirely, and does so as the first action of a given turn when it is selected for use. This is different from the Stun status condition in several important ways: It always works, and it has the top priority of any move in a given turn so it will always hit first, but it will only negate one of an enemy's actions instead of preventing it from acting at all for potentially several entire turns. Depending on your class setup, this is a great command for a supporting Adept to use to partially prevent a boss from damaging the party (it probably isn't a good idea to have Isaac use it when he should be focusing on dealing damage, though).

In The Lost Age, when Isaac's party joins Felix's party along with their returning Djinn (granted that Password data transfer is in effect), Ground's ability makes it a second Petra, a Venus Djinni findable as soon as that party enters the Great Western Sea. Just like Ground, Petra should be quite useful if handled properly, and both Ground and Petra together are equally usable. One particularly great use of Ground or Petra is in the third and final stage of the final boss fight against Doom Dragon; the two moves Doom Dragon is allowed to use will almost always both be extremely powerful and deadly, so preventing one of them will be a huge help in surviving the end of the battle. Another especially under-appreciated use of this effect manifests in the start of the Star Magician battle; Ground and Petra sharing the same priority as the Guard Aura monster skill the Guardian Ball uses to make the Star Magician invulnerable with means that if the user of Ground/Petra has higher Agility than the Guardian Ball (though the Guardian Ball has one of the highest agility ratings in the game, with 292 agility; this problem can be solved beforehand with Vine/Mud), the user can outspeed the Guardian Ball and make it unable to use Guard Aura with Ground/Petra, thus ensuring that the other three Adepts this turn can fully and safely make use of the strongest summons all together. This Djinni can singlehandedly make a very tricky and challenging optional boss battle much more simple than otherwise possible, in other words.

When you have both Djinn in your collection, the two together can completely prevent any enemy that only acts once per turn from ever attacking. While Adept One uses one of the two Djinn to freeze the enemy, Adept Two re-Sets the other of the two Djinn that was used to freeze the enemy in the previous turn, and the next turn Adept Two does the freezing while Adept One resets his Djinni. Adepts Three and Four, in the meantime, are the fighters who safely deal damage. This alternating strategy can be infinitely performed to ensure complete safety for the Adepts throughout the battle (though of course the battle would be a lot longer and more tedious this way). This is not as insanely helpful against any boss that can act more than one turn, though, since its second attack will not be prevented - and the reason this strategy never caught on is that none of the bosses following the reunion act only once per turn to begin with.

Name Origin
The words ground and earth are used fairly interchangeably (except when referring to the planet Earth). Jii is the Japanese word meaning ground or earth, making these names synonymous.