Takaroa

Takaroa (as it is known to terran explorers) or Diy'otun ("Storming Water" in Khalani) is an aquatic world that lies on the border of Umojan and protoss space. As no clear lines have been established between the two powers, who actually "owns" the world is nebulous, though it lies further into the protoss side of control rather than Umojan.

Haven of Water
The known history of Takaroa dates back to the exile of the Nerazim from Aiur, though xel'naga ruins hidden deep below the surface suggest the planet had a much earlier purpose even the protoss could not ascertain. Scattering through the stars, many Nerazim utilized the xel'naga's warp gate network to travel to distant and hidden worlds. One such place was a xel'naga outpost buried beneath the seas of a violent oceanic world, where waves can range anywhere from 40-80 meters tall, and supermassive hurricanes that can cover up to a fourth of the planet at a time. Despite mostly being covered in water and having an oxygen rich atmosphere, little life exists beyond microorganisms, plant and very basic deep aquatic animals due to these waves and conditions. The planet's two orbiting moons very close in orbit as well as its high gravity has created a cauldron of destruction even in spite of the planet being technically habitable for most life. Due to the planet's active tectonics, massive mountains peak out from the surface, creating some pockets of land.

The Nerazim, upon finding this xel'naga ruin safely preserved beneath the surface during exploration of the xel'naga warpgate network, named this outpost Diya'aril, Sanctuary of Water, and named the planet Diy'otun, Storming Water. Its location six warp gate jumps away from the central Nerazim shrine of Alys'aril made it so the perfect candidate one of the locations store replicated Ihaan memory crystals in a hidden haven, so should the main shrine fall the history of the Nerazim would not be completely lost.

Unfortunately, the Nerazim were unaware just how close to Protoss Empire space this warp gate had taken them. Forces under Judicator Kizrath, searching for xel'naga technology, tracked the signatures of a functional warp gate to beneath the world, only to discover it had been defiled by a Nerazim garrison. Before the Nerazim could even react, Kizrath unleashed a Purifier beam to blast open the crust over the shrine. Water poured in, killing all Nerazim within and destroying the xel'naga warp gate. No further attempts were made by the protoss to colonize or inhabit Diy'otun.

Takaroa
During the Umoja's age of exploration, two years prior to contact with the Confederacy, Umojan explorers found the violent world, ravaged by its massive oceans. They gave it the name Takaroa, named for the ancient Earth Polynesian god of the seas, and set up a small listening post in orbit to observe the effects of lunar gravity on oceanic worlds. This more some fruit in their fields of astromechanics, filling in some gaps of gravity knowledge missing from the archives of the Reagan. Though the Umojans noticed that some point in the last few hundred years there had been a discharge that evaporated a large portion of the planet's water in one location, and though the source alluded them the revealing theory was a meteor impact. The depth of which the xel'naga ruins were buried meant they never knew how close they were to evidence of alien life.

The planet was mostly left untouched by terrans outside of passive research, though the occasional thrill seeking thruster boarders, seeking a greater challenge than the Confederate's resort world of Miranar, would attempt to sneak onto the planet. Those that were caught were turned away by the Umojans there, though it's impossible to say whether some managed to avoid detection.

With the outbreak of the Great War, Umoja noticed how close Takaroa was to protoss space, and ordered a recall of all scientists working on the fringe for their own safety. Takaroa was abandoned by the Umojans, and though most stellar maps drew it as part of Umojan space, no attempts were made to reclaim their orbital research post as to not antagonize the protoss.

Dark Knowledge
After the End War, the rouge protoss faction, the Anakh'tum (Seekers of Twilight) uncovered ancient Nerazim maps speaking of the shrine on Takaroa. As they sought out ancient and forbidden Void knowledge, but were unwilling to do something so drastic as assault a populated shrine world, they moved on the planet, hoping that any Ihaan crystals survived the purification. Using their mothership's time distortion technology and antigrav generators, the Anak'tum were able to form a bubble around the exposed entrance to the temple. Survey teams arrived inside the xel'naga shrine, and to their surprise, though much of the technology of the xel'naga (including the warp gate) and the previous Nerazim were destroyed, there were indeed a great many Ihaan crystals that were not destroyed by the water pressure, particularly those sealed in the Forbidden Archives. Those they sought most.

Setting down beacons, they warped in a minor warp conduit from their mothership and used it to drain the water to the surface. Former Khalai Caset engineers repaired the planet's breech with a trillium alloy that could withstand the water pressure, then releasing the antigravity pocket in the middle of the ocean. An outpost was set up on the planet's surface, with gateways leading into the shrine, allowing them access and the ability to seal off the shrine on their terms if need be. The Anakh'tum then went to work researching the crystals there, using that outpost as a temporary operations center and even expanding the area around their surface gateway into a fully functional base.