Crystal

Location
Crystal is findable in the optional dungeon Yampi Desert Cave, an optional endgame dungeon accessible only with the Teleport Psynergy. When you eventually get to its area, you will find a group of sand on the ground where something under the sand appears in four designated spots in a predetermined pattern and at a moderately fast rate. Find a place where it appears, and at the moment the moving sand appears in front of you, cast Scoop - you can use the Select button to open the Psynergy menu and take your time casting Scoop while the sand pile is frozen in place by the fact that your game's Psynergy menu is open. Crystal is automatically battled once it is unearthed.

As an opponent
Statistically, Crystal has 990 HP, 94 PP, 309 Attack, 97 Defense, 280 Agility, and 33 Luck. Like all other Venus Djinn that are fought, in terms of resistance, it has a Venus Resistance rating of 193, Mercury and Mars Resistance ratings of 100 each, and a Jupiter Resistance rating of 25, and in regards to its abilities it uses its available Venus-based attacks with a Venus power rating of 125.

Crystal can use the following battle commands:
 * Grand Gaia: Used 53 out of 256 times, this is a Psynergy spell that strikes the party of Adepts with an eruption of earth-based energy and rocks from the ground, dealing a Venus-based attack with a power rating of 200 and a range of 5. This ability costs 32 of its user's PP.
 * Thorny Grave: Used 47 out of 256 times, this is a Psynergy spell that generates a mass of negatively-colored purple skull symbols that strikes into the party of Adepts, dealing a Venus-based attack with a power rating of 170 and a range of 3, and each affected Adept may be afflicted with the Haunt status effect. This ability consumes 24 of its user's PP.
 * Stone Spire: Used 41 out of 256 times, this is a Psynergy spell that causes five large stalactite to fall down from above onto the party and shatter, dealing a Venus-based attack with a power rating of 160 and a range of 3. This ability consumes 22 of its user's PP.
 * Nettle: Used 35 out of 256 times,
 * Wild Growth: Used 29 out of 256 times, this is a Psynergy spell that causes a large amount of thorny vines to erupt from the ground and though the party, dealing a Venus-based attack with a power rating of 110 and a range of 5. It consumes 19 of the user's PP.
 * Attack: Used 28 out of 256 times, this is this monster's standard physical attack, but for this monster it is counted as a Venus-based attack rather than a non-elemental attack.
 * Flee: Used 23 out of 256 times, this enemy has the ability to attempt to Flee the battle, thereby ending the battle if successful without rewarding you with the associated EXP, Coins, and the Djinni itself.

When defeated, Crystal yields 1211 EXP and 764 Coins, and the Crystal Djinni is added to your party's Djinn collection. If you fell it with an offensive Jupiter Djinni like Squall, its rewards increase to 1574 EXP and 993 Coins.

Defeating and earning Crystal in one turn without even needing summons should be trivial by this point if you have the Sol Blade from Mars Lighthouse.

Description
When Set, it increases base HP by 10, base PP by 5, and base Defense by 2.

When Crystal's battle effect is used, an elaborate, circular glowing orange symbol appears under the party's feet and rotates counterclockwise as orange energy is projected upwards through the party. All current battling Adepts have their HP meters restored by 50% of their respective maximum HP meters, making it superior to the otherwise similar effect shared by the Venus Djinni Flower and the Mercury Djinni Spritz.

Ability analysis
By the endgame, if you are playing with every Adept in their respective mono-elemental class series for example, Crystal suffices for Adepts such as the Venus Adepts that do not have the Wish Psynergy series or Mist Potions and need a decently powered substitute. Obviously this obsoletes the Djinn Flower and Spritz, but it is up to the player and their battling setup and approach how useful Crystal's easily understandable effect can be.

Name Origin
Crystal is a solid material, whose constituent atoms, molecules, or ions are arranged in an orderly repeating pattern extending in all three spatial dimensions.