Blackarachnia

Early Life
Elita One was a member of the Elite Guard. During her time there, Elita One befriended Magnum and Orion Pax. They weren't on the same teams, but Elita One often spent time with the two. But when Orion joined the rebels later known as the Decepticons, Elita One left his side. She didn't meet Orion again until he left the Decepticons.

When Elita One was with Orion at the library, History of Iacon. While being there, Megatron got to them and wounded Orion badly. Elita One then found Alpha Trion who helped rebuild Orion to Optimus.

Autobot
Elita One later joined the Autobots side by side with Optimus. The two even met Magnum, now Magnus. During the first year with the Autobots, Elita One met Sentinel Minor. The two got close, but during a mission with Sentinel and Optimus, Elita One was nearly killed. Organic spider-like creatures attacked and got onto Elita One. Sentinel wanted to save Elita One, but Optimus followed orders and took Sentinel out of there, leaving Elita to die.

Blackarachnia
Elita One didn't die though, she was infected and remade into a half-organic half-metallic creature. Now going by Blackarachnia, she swore to get her revenge on Optimus. She didn't do much until she heard of the Insecticon Project. This project created new bots. One of them being Waspinator. The two recreated the Insecticon Project, but now as Project Arachnid. They created a cross between metallic and organic lifeforms. But Autobot's commander, Optimus stopped this and took Blackarachnia captive.

After a while in prison, the medic, Ratchet started to help Blackarachnia to become Elita One again. This looked like it worked. She still had her Blackarachnia form, but with Elita One's personality. This changed though when Blackarachnia revealed she never changed but fooled everyone. She wounded Optimus and retreated. After this, Blackarachnia joined the Decepticons and fought with them until the Ark left Cybertron.