I thought the other times I've had this sentence (other forms of this question) that cailíní wasn't eclipsed (and that the discussion confirmed it was only in the singular that it was eclipsed). Is there something I'm missing?
It's a typo. Well spotted.
Why leis? Wouldn't it make more sense to have leo?
I retract my question.
I realise now that in this case, "leis" is just being used because it is followed by the article.