So according to this ruling:
viewtopic.php?f=59&t=77143
I can play this with no opposition, correct?
Flanked by Nightmares
A topic from AEG's L5R CCG Rules forum, copied for Oracle of the Void from a copy of the forum saved in October 2015, so pages it didn't save are missing. Players' names are left out; the rules officials are named. Rulings are as they stood on these dates; later rulings, the rulebooks and the Rules Archive may differ.
Yes, you can take the Battle action on Flanked by Nightmares if you control an unbowed Shadowlands Personality who is unopposed at the current battlefield. Its effect fails so the action is not successful.