Whispering Shadows mandatory for secrets?

[Lickmajora]

or can we find them by just being thorough and manually checking everywhere?

[mpnorman10]

You can buy the spell at vendors. I always thought I needed them (if nobody in the party can learn dark magic).

The RPC (recruitable player character) for one of the quests gives you automatic detection while she is with the party. That helps early on, but then she is gone and cannot be recruited again.

[Traul]

There is another RPC that can find secrets for you later in the game. You can just skip secrets until you find it, then come back to the dungeons. Besides, secrets are only found in dungeons. You can clear the outside world first.

[Lickmajora]

i tested it. dungeon secrets are only accesabale and "findable" with an RPC or Whisper Shadows. If you have neither, the secret cannot be unlocked even if u know its wherabouts