I think Archangel is right. This Arc does just appear to be filler fanservice. Maybe the series is ending soon. There doesn't appear to be too much thought into it.
"Oh no! They have all the magic artifacts. What will we do?"
"It's impossible--but wait--aren't we forgetting the secret magic artifact?"
"Oh yeah, but how do we get it there?"
"Why don't we use plot device?"
"Cheers"