Similar word to portentous:
alarming, amazing, apocalyptic, astounding, augural, destined, doomed, exhilarating, extraordinary, fated, fateful, haunting, ill-boding, ill-fated, impending, important, inauspicious, inspiring, intriguing, ominous, phenomenal, premonitory, prophetic, remarkable, suggestive, threatening, thrilling
alarming, amazing, apocalyptic, astounding, augural, destined, doomed, exhilarating, extraordinary, fated, fateful, haunting, ill-boding, ill-fated, impending, important, inauspicious, inspiring, intriguing, ominous, phenomenal, premonitory, prophetic, remarkable, suggestive, threatening, thrilling