It looks EXACTLY like the traveler
https://youtu.be/Ssnw2GA657s
Spoilers for end of halo 5. Watch at your own discretion children of the light
[spoiler]skip to 2:40 https://youtu.be/sXaSTvCIjgU[/spoiler]
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Requiem, the sphere that the Didact was contained in at the beginning of Halo 4, was also a Cryptum.