User blog comment:Cat.ion0/Elgif dungeon results/@comment-26926725-20151210144014

It s 20% for the lowest rarity Elgif. The hgher the rarity, the lower the capture chance.

I think that the capture chances are multiplicatively lower with each rarity. So capturing a good 6* or 7* Elgif is no timpossible but very, very improbable. If you get a caprute, it'll probably be a low rarity and bad ES.