Lucid → (adj) Mentally healthy: compos mentis, rational, sane. Idioms: all there, in one's right mind, of sound mind. Admitting light so that objects beyond can be seen: clear, crystal clear, crystalline, limpid, pellucid, see-through, translucent, transparent
Enigma → (n) Anything that arouses curiosity or perplexes because it is unexplained, inexplicable, or secret: conundrum, mystery, perplexity, puzzle, puzzler, riddle
Opaque → (v) To ease the anger or agitation of: appease, assuage, calm (down), conciliate, dulcify, gentle, mollify, pacify, propitiate, soften, soothe, sweeten
Zeal → (n) Passionate devotion to or interest in a cause or subject, for example: ardor, enthusiasm, fervor, fire, passion, zealousness