Universum Control CenterThe exact date of creation of Universum Control Center is unknow but it is known for sure it was created before the hero appeared in the Rogue Encampment and most possibly it happened after high demons defeat in the Burning Hell civil war.
Baal has accumulated all his power and knowledges of science and Universe inner construction to create this unique device. UCC allows Baal to reverse the time flow and return to the past to try to defeat the hero which pursues him. It seems that Decard Kein is wrong telling UCC was created in the ancient times, otherwise why would not Baal use it during the Hell demons rising and defeat from the Horadrims in Sanctuary.
It also looks like the Universe inertion is so huge that even returning back in time Baal can't make major changes and just hopes one of his minions will succeed in destroying the hero. However, UCC makes Baal almost unbeatable as he can create temporal loops every time and will not be defeated ever.
The time loop affects Sanctuary and elemental planes and it is unknown it the other Universe involved into this process. It is also unknown if memories about previous loops are preserved. It seems that Baal keeps full or partial memories, most powerful angels, demons and human mages keep partial memories and all others keep just misty feelings.
There is no information how many times Baal has created temporal loops - it could happen thousands of times and end the same over and over again.
Decard Kein and Tirael look for the way to create the second UCC by unifying all elements in the Universe - the fire, the water, the air, the earth, controlling synapse, pure emotion and organic cell… The hero should seek for these elements during all his jorney and finally he will be able to assemble his own UCC.
What will happen when two ultimate controlling devices will conflict? Nobody knows. There are two equally possible ways: either Sanctuary will be destroyed along with other neares worlds or Baal will be unable to reverse the time and there will be last battle that will finally deliberate the world if the hero will succeed.