You may be looking for:
Ehlna (translated as "Haven") is a moon inhabited by the Alysaar. The moon contains a strange energy with two strongest points; one under the sea and one on land, where the Alys'aril ("Sanctuary of Wisdom") was built. The energy changes khaydarin crystals, which allows the Alysaar to store memories within the crystals.
The energies are found at three locations on Ehlna; one under the Alys'aril, one deep underground (where a large number of modified khaydarin crystals are found) and one underwater; Ulrezaj secretly visited the latter when he became a dark archon to replenish his energies.
Shortly after the Nerazim were banished from Aiur, their xel'naga vessel and small fleet of protoss vessels discovered Ehlna. Discovering a xel'naga-crafted warp gate, the Dark Templar settled there. They discovered a source of khaydarin crystals, which had been modified by combinations of energies to hold memories. Lacking preservers of their own, the Dark Templar stored these at the Alys'aril.
The Dark Templar remained there for two centuries. Eventually the majority of the Dark Templar left, but some, the alysaar, remained. Dark Templar would frequently visit Ehlna on pilgrimages to have their memories copied. The Dark Templar left three ships on Ehlna, one of which was capable of interstellar travel.
In 2503, fugitive terran Jake Ramsey arrived on Ehlna, trying to solve a unique problem – he was carrying a preserver, Zamara, in his head, and it was killing him. Zamara had crucial information she had to deliver to the protoss. She intended to store herself in a powerful khaydarin crystal carried by Ramsey. However, she was sought by Ulrezaj (a powerful dark archon terrorist), the Zerg Swarm and the Terran Dominion. In pursuit of his enemy, Ulrezaj returned to the world on a xel'naga vessel, followed by Ethan Stewart, an infested terran commander subordinate to Sarah Kerrigan, who was in turn secretly followed by Terran Dominion vessels under the command of Valerian Mengsk, archaeologist and heir to the Dominion throne.
In the Alys'aril, Ramsey underwent a long psionic ritual to remove Zamara's essence from him. As he did so, Stewart's forces appeared and surrounded the facility. Selendis convinced him that Ramsey was undergoing the ritual to save his life, so Stewart intended to wait until he could strike... after sending a hydralisk spy to watch over Ramsey. Meanwhile, protoss forces recently arrived from Shakuras along with Ramsey's companion Rosemary Dahl began to package the crystals for transport back to Shakuras. However, the uneasy peace was broken by Ulrezaj, who forced Stewart's hand. Battle errupted and while the Dominion gained the upperhand, they were later forced to retreat when the protoss returned in force.
Ehlna was a dust filled moon, and had a blue-green sun. During the planet's sunsets, the skies would change from yellow, to orange, to purple, and slowly to grey. The climate was arid and very hot, and the protoss who labored there would only leave their halls to gain nourishment from the nearby star.