This is an interesting topic. Never really thought of it before now since no one ever worshipped the Ellimist or Crayak, at least not to my knowledge. I haven't yet read the Ellimist Chronicles, or even all the Animorphs books (SHAME ON ME, I know...). I do see the correlation between Ellimist and God (whatever they may be to you), Crayak and Satan. In the Bible, God and Lucifer have played at least one game that I know of, and it's in the book of Job, if I remember correctly. For those who may not know of the story, Satan bets God that if he took away Job's belongings, friends, and family, Job would rebuke God and swear him off. Of course, Job is remains faithful and prays to God, so God wins, per usual. And I'd say Job loses, but that's just my opinion.
It's a messed up game they play, just as the Ellimist and Crayak do.