What's the purpose of the tool?.
Please leave more detail info in your description, reading and trying to figure this tool out will give us tumor.
That's a Crypter used mostly to make any virus, rat and keylogger undetectable from several antivirus.
I don't know how OP can say that using it with any malicious tool is not allowed since those tools are very often made especially for this purpose.
He even says "scan files only using the built-in scanner", because most file scanners will share their results and samples with other antivirus, making the program more likely to be detected in the future.
Generally, antivirus work by splitting source code of application and then search for certain string within source code.
If antivirus detects any certain malicious strings, it either stops the scan or deletes the file as virus from system.
Thus a crypter basically makes an infected file FUD or UD by encrypting it.
https://way2h.blogspot.com.br/2013/02/what-is-crypter-how-it-works.html
