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.
Serenity reads; Battle/Open: If this card is in play, target your Personality and, if this is the Action Phase, discard a card: Straighten him.
Death of the Winds reads; Battle, (2) : Target your unbowed Tactician. Search your Fate deck for a non-Unique Battle Strategy and take an additional action to play it.
Can I use Death of the winds to search for Serenity? I assume I can't put into play.
Thanks for your time.
Yes. It can be searched (but not played).
Clarification: As Death of the Winds doesn't give any other option to the player than to "play" the searched card, if the card cannot be legally played at that moment, it is discarded instead.
See here If an effect directs a player to search for a card and do something with it (such as play it or put it into the hand), and that thing fails, the card is discarded instead.