hmm, it only just now occurred to me to look sempiternal up, to see if it can stand on its own as an adjective, and the etymology (from Latin sempiternus : semper, always + aeternus, eternal) suggests that the word is self-redundant.

i doesn't make sense that it can be superlative to 'eternal', since there can be nothing beyond eternity. in what context would one use 'sempiternal' as opposed to simply 'eternal', except as a symptom of euphuism?