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.
According to this: viewtopic.php?f=59&t=77154&p=1013374&hilit=Flanked#p1013374 About the "Armor of Heaven's" part.
The Rules Team says it won't work because it says "another player's target".
What about Blessed Tessen? It says "another player's ACTION". Does it works?
Blessed Tessen: Reaction: After another player's action targets this Personality, bow this card: Gain 2 Honor after the action's resolution.
According to this: viewtopic.php?f=59&t=77154&p=1013374&hilit=Flanked#p1013374 About the "Armor of Heaven's" part.
The Rules Team says it won't work because it says "another player's target".
What about Blessed Tessen? It says "another player's ACTION". Does it works?
Yes, Blessed Tessen can react to Flanked by Nightmare's targeting. Unlike Armor of the Heavens, Tessen cares about whose action it is, not who does the targeting.