No, it's not. It's scientific. It's man-made, and you don't need magecraft to use it.

[Kerry is sure Diarmuid doesn't know a thing about science, but he says this anyway.]

These people kidnapped us, it's obvious. They said they needed us. They don't want us to know how they did it, that's all.

There aren't any fairies around, and this place doesn't have anything to do with fairies, so that makes no sense. Just because fairies are all you know about doesn't mean they did it.

[He doesn't mean to sound rude, he's just telling it like it is.]