New Appendix profiles

It has been a little while but I'm contributing a few profiles to the Appendix now and then. Here's three new entries I created: 3-21 (a Captain America foe); Viking (a Hulk foe); and Mark 12 Sonic Depressor (a Hulk device). I'm always happy to continue my involvement with the Appendix and hope I'll have more to share in the future!