Cybermen are, as their name suggests, men that have been cyberised. Instead of being part-man part human like some Sith Lords we could mention or something from the Delta Quadrant, the Cybermen are merely robot cases with human brains wired into the top. Along with the Daleks they are the worst enemy of the Renegade Time Lord known as the Doctor. They have no emotion at all and they all think alike. They can attack using electric shock-blasts from their hands or lasers in their arms. They are led by CyberLeaders.The League cast them into another universe to prevent them from causing harm. Despite this they still manage to escape on several occasions, but when they do its always when the league need that extra bit of military force so they often end up fighting with the League, the Humans and the Daleks, not against them. An example of when this has NOT occured would be the Dalek-Cyberman War.
Despite being weaker than Daleks they are significantly stronger than Humans (but then again, who isn't? Quarians aren't), with the average Cyberman being ten times stronger than an average Human (Although they are not as strong as Spartans). However, they are vulnerable to electricity and high-pitched noises. Rumour has it that some Cybermen are even vulnerable to the element Gold.
However, after their war with the Borg the Cybermen made significant advances in technology and methods. They assimilated Borg components into themselves in order to become more powerful, and it worked. Cybermen wer given an ultimate upgrade which the Cyberleaders called the 'Assimilation' Upgrade, which allowed Cybermen to become resistant to different forms of attack. Since then, the Cybermen have evolved to be much more effective in battle than they previously were. After this upgrade, their conquest increased by leaps and bounds and, since their intelligence also increased, they swore alleigience to The League, recognising that it was futile to oppose it and they could gain so much more by joining. Now, they stand as a powerful addition to The League Military's already formidable might.
Cybermen have been divided into three notable segments determining their origin:
Cyberman Remnant, being parallel Cybermen made in our universe
However, after their war with the Borg all of these factions joined into one, making one superace of Cybermen.
A rather embarrassing defeat for the Mondasian Cybermen at the hands of a Raston Warrior Robot.
The Mondasian Cybermen, in their earliest form.
The defeat of the Mondasian CyberController at the hands of the Sixth Doctor.
The Head of a Cyberman Remnant Cyberman attacks a ginger scottish lady.