Professor has lived a long and complicated life...
In his early life, he was quickly recognised as a prodigy, with incredible intelligence. His continued rise through the ranks of society was fast, and remarkable. However, it became too much for him. The degree to which he outclassed all others came back to haunt him. He made huge advances in multiple fields of science, he brought an age of peace to his land and all was happy.
But people demanded more. Unsatisfied, expecting him to continue to produce the kind of results that had come before, they demanded more...and more...and more. It drove him mad. Unable to bear the pressure put on him by the ungrateful people that surrounded him, he cracked. His creations turned on everyone, slaughtering tens of thousands of people who had come to rely on him so much. The world ran red with blood, and all that was left by the end was a barren wasteland with a single, vast laboratory in place, so he could continue his work.
However the Professor is never satisfied. His lust for power was insatiable, and so he left his home and ended up in the Nexus, back in the days of the old Town. He joined KNAVES, using them as a place to work away quietly, and safely, while acting like he supported their goals totally. Numerous attempts to take over the town took place, the police were engaged in a near-constant war with them, and Affidavit produced some of his finest work there including the infamous liquid agony.
However, nothing lasts. Eventually KNAVES fell apart. Their leader left, and without him, the fragile bonds that held all the members together were shattered. Very little blood was spilled, but continued co-operation was impossible. They all went their separate ways, and Affidavit found himself lost without the security that KNAVES had provided for so long. He wandered, joining several organisations briefly but never lasting, finding them all to be lacking the same appeal that KNAVES had.
Then, in enupnion town, Affidavit briefly joined forces with Magtok. It turned out to be his first serious mistake. Magtok's plans and inventions were treated with disgust by Affidavit, and he openly claimed that Magtok was not a proper scientist, and unworthy of being leader of any organisation of any sort. After several arguments he was kicked out, and shortly afterwards Magtok sent out an assassin to kill him.
Hannah, as she is now known, slit the Professor's throat and killed him within moments. However, Affidavit is one of the most paranoid people around. He had made plans, even for his own death, and his mind, his thoughts, his consciousness was split among the hundreds of creations in his service. Driven mad by the sudden rush of power (as has happened further in the past once or twice) he initially tried to get his revenge on Magtok, before calming down and simply resuming his normal work.
Nothing, however, has ever given Affidavit the same thrill as his time in KNAVES. He still treats his KNAVES uniform with respect, and still thinks of himself as the second in command of one of the greatest organisations ever to terrorise the Nexus. That's what he remembers KNAVES as anyway. More to the point though, his continued searches for something to replace KNAVES all proved futile, and so, he planned a return to the castle.
Now, he's back, at the KNAVES castle once more. The deserted, hollow, damaged remains of the KNAVES castle anyway. He dreams of making it great again, a goal that is both foolish and unachievable. However, at the very least the KNAVES castle is the perfect site to live out his fantasies, to let himself feel like he's part of the long dead organisation once more.
And now that he's back, his experiments can begin properly once more. Some of them may well be repeats though as his travels have resulted in the loss of the odd creation before he could withdraw from its mind, and as a result several of his memories have been lost.