Which castle can’t be taken by a Necropolis on day 111?

Someone was developing a tactic for taking a Crypt behind a Tower using un-upgraded Goblins for some kind of fix. Here's an idea, practice it :)

I've seen something like this online. I played with one foreigner in a 2v2 match – he didn't upgrade his Goblins, and I thought he was a noob... but he turned out to be a super-pro.