Gholos was a gestalt species from Golos.
Gholos took the form of a cloud of gas. It would change colour to suit the occasion; pink normally, red when scared or shocked and blue when attacking. This blue attack, known as "the blue sting of Gholos", could easily kill a human.
Gholos was a gestalt entity, able to divide itself into smaller forms. Spending time away from the gestalt was tiring and complete separation was deadly. It used a highly complex language to communicate. It sometimes took decades for an outsider to learn this language. (AUDIO: Bang-Bang-a-Boom!)
The Gholos and the Angvian empires were close to each other, leading to territorial disputes. The Angvians claimed their pastoral colonies were attacked by the Gholos, forcing them to go to war. Though peace treaties were made, the Gholos eventually broke them. Likewise, an agreement about the Zordon Nebula was broken by the Angvians. This led to centuries of war.
Eventually, peace was wanted between Golos and Angvia. In order to prevent attacks from Angvian terrorists, two peace conferences were held. One was held on Achilles 4, which was the obvious target. The second was actually the 309th Intergalactic Song Contest at Dark Space 8. The ambassador would have the political information telepathically hidden until they needed to know it.
Despite these measures, the secret got out. Loozly, the translator for the Gholos competitor/ambassador, didn't want peace and tried to disrupt the Song Contest, killing people using Angvian methods. The Gholos eventually learned the truth, but was unable to communicate it and threatened by Loozly with a special device. Eventually, the Seventh Doctor learned the truth and was able to get the device deactivated. When Loozly realised he had lost, he tried to hold the Angvian ambassador hostage. Gholos killed him, saving her and leading towards the peace conference. (AUDIO: Bang-Bang-a-Boom!)