It is stated through implication that the Shu'ulathoi were eventually found by the Combine and assimilated.
It is also stated that the Combine Advisors are the infantile Shu'ulathoi, as their psychic prowess grows greatly with age- something that the Combine strangely does not want, and so it can be inferred that the life support that hangs off of these creatures also halts the aging process. It is stated that they were a species much like humans but began to modify and augment themselves greatly until they became reliant on these technologies to survive. Their bodies have undergone heavy mechanical modification, judging by their reliance on life support pods, mechanical arms and special harnesses to keep them afloat, and are seemingly incapable of sight (as evidenced in Episode 2) and likely require their cameras to see things visually. They are large, grub-like beings with no natural appendages or eyes, a small, hole-like mouth with a long tongue strong enough to pierce through flesh and bone, presumably with a small hole within capable of sucking out brain matter. They possess immense psychic powers not limited to telepathy and telekinesis.
The Shu’ulathoi (unknown meaning Mentioned by Vortigaunts), also known as Combine Advisors serve as a high-ranking role - if not leadership role - within the localized Combine governments across planets and universes.
