I'm noining the superior side of the Old Ones, and I'm going to use some of knowledge of alien progression in enemy unknown through the
Long War modification to the game. One of the earliest advancement the aliens try to create is a small flying scout drone; while this is a good idea, gives us some basic knowledge of artificial intelligence, hovering technology, machinery (maybe biomechanic technology in the future, and more)
Also I would love if we advanced the flying scout drone into a Combat Hunter-Killer Drone that had ability to cloak, have advanced A.I, had an electromagnetic pulse it emits that creates a shield around enemy fire from kinetics to energy weapons, and lock-on missiles!
So with our first design let me suggest a design to allow those innovations to take place.
Scout Drone: A small drone (about the size of a basketball) that utilizes tiny amount elerium to pulse so that it hovers over the ground, and can emit more of the elerium fuel to fly distances of 5-10m off the ground and than hover on its new flying position. Equipped with advanced photoreceptors so that it can track the location of enemies and notice movement in the visible color spectrum, and a shock taser probe Gun on the frontal head of the Scout Drone that horrifically stings when it attacks a biological unit, equipped with a heavy amount of sedatives to make the organics to pass out for future experimentation. The Drone is quite small and can fly, with some maneuverability but this isn't the priority of the design, which makes it a difficult target to hit but is very lightly armored and can't handle attacks from kinetic-based weapons. It would serve as the scout/reconnaissance role for the aliens and maybe has some ability to act as a light skirmished during combat.
Also let's be Terror From the Deep Aliens and have an underwater fortress or something, needs further elaboration from me.