The Cloven Crystals are magical items that resemble an amber cat's eye. The Crystals are critical to releasing Uk'otoa, acting as keys to its confinement. It rewards those who use Crystals to free it with control over water.
The Cloven Crystal has an amber-yellowish color. It has striations that refract light around it. At one end, there is a pointed oval line carved in about three inches across. With all three crystals deposited, Uk'otoa can be released to rule the Lucidian Ocean once again, just as it had done in ages past. Avantika deposited one Cloven Crystal on Urukaxl; Fjord deposited one Cloven Crystal in the Gravid Archipelago temple; the third is in Fjord's possession.
Fjord had a vision of Vandren absorbing a Cloven Crystal after killing its previous owner. The accuracy of this vision is seemingly confirmed by Avantika telling Fjord Vandren already had a Cloven Crystal when they met.
Avantika and Vandren discovered another Cloven Crystal was being auctioned off in Port Damali. They stalked the collector who bought it to an unknown island and killed him. Avantika absorbed the crystal, causing Uk'otoa's eye to appear in her palm.
"Lost Treasures" (2x22)
In the subterranean tunnels under the Labenda Swamp, the Mighty Nein found a Cloven Crystal resting in a pool of water. Fjord went to touch it and immediately entered a dreamlike trance, during which he saw a vision of his mentor, Vandren, standing over a body, thrusting the Crystal into his chest, and summoning the same falchion that Fjord wielded. Fjord also thrust the Cloven Crystal into his chest. After this incident, the falchion appeared to have a Cloven Crystal resting within it.
"The Journey Home" (2x30)
"Dangerous Liaisons" (2x37)
"Dubious Pursuits" (2x40)
"The Diver's Grave" (2x44)
After failing to find the third Cloven Crystal upon the wreckage of the Tide's Breath whilst exploring the Diver's Grave, Fjord later discovered and absorbed the Cloven Crystal within the lair of Dashilla. His falchion now had two eyes, one in the hilt and one in the pommel.
"The Second Seal" (2x47)
After the Mighty Nein defeat the Deep scion and Chuul guarding the ruined temple located underwater at the Gravid Archipelago, Fjord deposits one of his Cloven Crystals at the location and is rewarded with the power to control water. Uk'otoa also gifts Fjord a vision of the third and final temple's location. 
- ↑ See "Lost Treasures" (2x22) at 3:01:46.
- ↑ See "Dubious Pursuits" (2x40) from 3:01:29 through 3:02:44.
- ↑ See "A Hole In the Plan" (2x42) at 3:25:19.
- ↑ See "Lost Treasures" (2x22) at 3:11:05.
- ↑ See "The Journey Home" (2x30).
- ↑ See "Dangerous Liaisons" (2x37).
- ↑ See "The Diver's Grave" (2x44) from 3:53:48 through 3:54:54.
- ↑ See "The Second Seal" (2x47).