Dominators

"That is not the name of a species that comes in peace."

- Wally West

The Dominators are a race of extra-terrestrial beings and conquerers.

Earth One
In 1951, the Dominators landed on Earth, abducting humans to gather information about them. They attacked, killing hundreds of soldiers. Unbeknownst to them,Steel, Heat Wave, and Vixen arrived and subdued a straggler. Suddenly, the NSA appearred and took them into custody (including the Dominator).

As the Legends begin to interrogate the captive Dominator, Smith appears and has the Dominator pinned down onto a lab table while experimenting on them. This results in the NSA forming a truce to keep the equilibrium of Earth balanced.

Sixty-five years later, however, with the appearance of Meta-humans especially Barry Allen, the Dominators returned to Earth, prefaced with a warning to Earthly authorities that they meant no harm, though in fact planning war. Four ships crash landed, one of them in Central City, spilling forth with Dominators. This faction kidnapped the President and set up a mind control device in an old salt mine, but this device was eventually destroyed by Supergirl, with the help of The Flash. However, they soon abducted Sara Lance, John Diggle, Thea Queen, Ray Palmer and Oliver Queen, placing them into an induced dream world. They eventually escaped, fighting against the Dominators, before escaping in a pod. As they headed down towards Earth, the mothership followed them. At this time, the Dominators were about finished with their superweapon that they intended to use to wipe out all metahumans on Earth. They threatened to drop it unless Barry Allen surrendered himself in 24 hours, which he refused.

They descend the mothership down on Central City and begin to drop the metabomb, while a platoon of Dominators fight the heroes on top of the STAR Labs hanger. Barry places the high-frequency trasmitting devices made by Martin on the Dominators, and Felicity detonates them, effectively taking them out.

The bomb begins descending, with Sara in the Waverider attempting to use the ship's tractor beam to hold it up. Firestorm arrives and uses his powers to transmute the bomb into water, successfully saving the planet. The mothership then flies off into deep space.

Earth Thirty-Eight
Sometime before Kara Danvers was born, the Dominators traveled to Krypton and performed experiments on a number of people, as well as killing a lot more.

Powers

 * Super strength: The Dominators were said to be really strong, overpowering inhabitants of Krypton, although Kryptonians usually don't exhibit superhuman attributes under a red sun. Their strength was also shown as a Dominator hit Oliver, sending him flying off the roof of a building.
 * Telepathy: The Dominators are able to communicate telepathically with others, seemingly also being able to use their own language, despite languages such as English not being their native language.