Mutants are controlled by the genocidally insane Artificial Intelligence, Morgana, in her plan to claim all the Emitters and reprogram them to xenoform the planet into one more suited for mutant lifeforms (extinguishing human life in the process). Any Clan that occupies an Emitter will have to defend it from increasingly powerful waves of Morgana's Mutant hordes, in addition to rival Clans. With each successful defensive battle against the Mutants, your forces will extract and store Antigen from fallen Mutants within the Emitter. This can be then be used to convert your forces into powerful A-Mutants.
A-Mutants boast considerably higher defensive and offensive statistics, in addition to costing far less to maintain than your regular forces. All Antigen that your Clan recovers from defeated Mutants is stored within the Emitter where the battle took place. Antigen can only be used by Clan Members who had Units participating in its defense, and who have been authorized Antigen access privileges by their Clan's Clan Leader or Deputy Clan Leaders.
A-Mutate different Unit types by upgrading an Emitter's level:
Level 2 - Infantry
Level 3 - Armored Corps
Level 4 - Artillery
Level 5 - Air Forces.
Bear in mind that an Emitter will attract more attacking Mutants with each additional upgrade level. This in turn will provide you with more Antigen, with which you may create more A-Mutants.
Clan Leaders and Deputy Clan Leaders may redistribute antigen between Clan Emitters at their discretion. Note that the amount of Antigen lost during transfer will vary depending on the Emitters' relative development levels and distance.
Send Troops to one of your Clan's Emitters and open the A-Mutation window. Select the number and type of Units you wish to A-Mutate, and press 'A-Mutate'. You can review the Emitter's 'A-Mutation' history from the 'A-Mutation History' window in the Emitter interface.