Since Kefka exiles the spells before casting them, we can exploit Rakdoss many cast-from-exile synergies like Prosper, Tome-Bound and Passionate Archaeologist to extend the value further
That card is Pete, and hes a godsend for Sapphire/Steel, helping it fair better against just about every other deck out there, but especially against Ruby decks
Consider Arthur Novice Sparrow, who can deal with early-game threats or be used for your Sing Together songs to bypass his Reckless
You don't even have to control four or more legendary creatures when you activate it
Plus, Inalla's tap ability to deal damage to opponents provides a useful win condition, synergizing well with cards like Intruder Alarm that can repeatedly untap her for exponential damage
These days most decks don't have enough black cards to be able to comfortably pitch to this nor do they have enough reliable card draw to easily stomach the two for one