Les Scrins

The Scrins, Aliens or Visitors are a race of aliens that appeared halfway through the Third Tiberium War, following the destruction of the Prime Temple by the GDI using the Ion Cannon (Again... That’s a bit much, isn’t it?). Because this was part of Kane’s plan:

“According to Tacitus, an explosion of liquid Tiberium could attract a Visitor ship… But none of our experiments have ever caused an explosion powerful enough.” – Kane revealing his true plan to the Nod Commander (the player) during the Brotherhood of Nod campaign

Thus, emerging from the shadows of Neptune, the ships of a harvesting vanguard – the Scrins – arrived to begin “the Harvesting Process”, armed with plasma weapons, extraordinary vessels and other technologies from the stars.