| braintwister(difficulty, question, secret, puzzle, subtlety) |
| charade(question, secret, puzzle, subtlety, mystery) |
| chiller(difficulty, question, secret, puzzle, subtlety) |
| cliffhanger(difficulty, question, secret, puzzle, obscurity) |
| cryptogram(difficulty, question, secret, puzzle, obscurity) |
| difficulty(question, secret, puzzle, obscurity, subtlety) |
| dilemma(noun, trouble, challenge, puzzle) |
| grabber(difficulty, question, secret, puzzle, perplexity) |
| head-scratcher(noun, trouble, challenge, brainteaser) |
| inscrutability(difficulty, question, secret, puzzle, subtlety) |
| inscrutableness(difficulty, question, secret, puzzle, subtlety) |
| mindboggler(difficulty, question, secret, puzzle, subtlety) |
| occult(difficulty, question, secret, puzzle, subtlety) |
| oracle(difficulty, question, secret, puzzle, subtlety) |
| perplexity(noun, difficulty, question, secret, puzzle) |
| question(difficulty, secret, puzzle, obscurity, subtlety) |
| rebus(question, secret, puzzle, subtlety, mystery) |
| rune(difficulty, question, secret, puzzle, subtlety) |
| secrecy(difficulty, question, secret, puzzle, obscurity) |
| sphinx(difficulty, question, secret, puzzle, perplexity) |