The Caretaker was the name given to the ancient Rakata whom has for thousands of years been the caretaker for a group of Kumumgah in a hidden underground city on a unknown planet. The Caretaker, whom forgot his own name over the years, was a Rakata scientist who established a secret colony of Kumumgah at the edge of wild space in the Filo Universe after the original Kumumgah homeworld was blasted into glass by the Rakata of the Infinite Empire when they rebelled against the Empire. The Caretaker felt something most Rakata do not feel, regret and shame. He vowed to preserve the colony of Kumumgah. For the next 27,000 years, the caretaker provided power and protection to the isolated colony.
In roughly 1500 N.E. the Caretaker learned he was dying, having reach the absolute limit of Rakata technology and force energy to preserve his existence (it turns out the nanoprobes that had the effect of extending everyone elses lives had the adverse effect of killing the caretaker due to technology and force energy he already used to extend his life). The Caretaker began bringing ships and their crews this his array to prefer experiments on them to try and find a way to extend his own life, all his experiments proved to be failures. Most died instantly, a few managed to live for a few days before dying - which he sent to live with the Kumumgah.
By 1518 N.E. it became clear he was going to die before he found a cure and started stock piling energy for the colony, but performing a few last test. At one point he brought the USS Voyager to his array and experimented on a few of its crew, but by then he was so close to death he limited his experiments on a few.