Nikolai Andreyev (known as the Warlord, Patient 0, or Legion Champion) was a decorated Commonwealth soldier. After the death of his family, he donated his body to science and he has become notorious for being the first subject of the failed Agent Omega program.
Andreyev is the main antagonist of the Sonoran Desert missions, along with his ex-Commonwealth legionaries. He appears as a boss during the final Sonoran Desert mission, Between Life and Death. Most dialogue will refer to him as "the Warlord" or as "Patient 0", later using his real name and explaining his past in-depth. In medium security missions, Andreyev appears as the Legion Champion.
Prior to Agent Omega, Andreyev was a decorated Commonwealth soldier. Sometime during the 2140s, his wife and child were killed in a "terrorist attack" organized by the Allied Revolutionary Militia (ARM). He never fully recovered from the incident and later donated his body to science.
In 2145, the Agent Omega program was opened by the Commonwealth and selected Andreyev as its first test subject (designation: Patient 0). The goal of the project was to create the perfect agent: one who is faster, stronger, and even smarter than any human in history. Research and development of the project was undertaken by a team of five Commonwealth scientists. These scientists developed a serum (known as the Agent Omega Serum) and injected Andreyev with it.According to the scientists, Andreyev became violent and uncontrollable after the injection. He mutated and it wasn't long before it was apparent that he had lost his sanity. After the failure of the project, the committee in charge concluded that Andreyev should be dumped in the Sonoran Desert. One of the scientists supported the decision, while the other four were imprisoned for their dissent (they were later released by Bancroft). That same year, the Commonwealth organized his release, tasking a team of Commonwealth soldiers with the escort of Andreyev to the Desert. In order to keep him under control, it was necessary to frequently change his IV with a serum consisting of his own blood and a concentrated sedative.
The fate of the Commonwealth crew escorting Andreyev isn't clear. The ship obviously reached its destination, as its remains are found decaying near the ruins of New Yuma. The most likely possibility is that the crew stayed behind and became Andreyev's underlings in the Desert, presumably being the foundation for the Legion. Other possibilities could be that he escaped and killed the crew, or that the crew left the ship and Andreyev behind after arrival.
Following his release, Andreyev began to assault the many tribes of the Desert. He quickly earned the name the Warlord, for the bloody campaigns he brought to those in the Desert. One tribe, the Kanar, was conquered by him shortly after his arrival. The Kanar and the Legion dominated the region for the next ten years, and directly threatening Junk Town and Dome City.
In 2155, one agent (the player) who had been liberated was found to have been injected with a modified Agent Omega Serum, signaling that the program had been re-opened. In an attempt to create a cure, the agent tracked down and killed Andreyev to obtain a DNA sample to prevent themself from mutating and becoming another Andreyev.
Andreyev appears primarily in the Sonoran Desert mission Between Life and Death, and also in medium security PvE missions, labeled "Legion Champion". His PvE mission map is Shifting Sands, which is nearly identical to the Sonoran Desert mission.
In both appearences, Andreyev is equipped with a large, sharpened blade that is capable of vaulting shockwaves at enemies. The blow from the blade is also capable of stunning not only players, but also mechanical objects such as turrets. In addition to his blade, Andreyev carries a modified minigun that is also capable of firing missiles at his foes.