Swamped

"Maybe this is a dumb question," you say. "But if there's a spell hiding whatever-it-is, how do you know it's pulling the ship down?"

"Ah, that's actually quite observant of you," the wizard says. "The short answer is, I could tell because I was watching this symbol. And that means I could see what it was doing. In that process, I was able to notice another force doing exactly the opposite. Imagine that this spell is someone pulling on a very long rope, and something else is pulling on the other end of that rope a long way away. If I touch the rope without pulling, I can feel the other force very clearly. But figuring out anything else about that force is quite difficult."

"And let me guess," Resk grumbles. "This isn't an actual rope you can follow to the other end."

"Not quite, there is something analogous. The problem is that I'd probably fall unconscious first. So, about the same overall situation," Wiz says with a shrug.

"Could you make a spell follow the rope?" you ask. "Again, maybe that's a stupid question."

"Well, it's understandable with the simplified explanation I've given. I compared it to painting over house numbers, but that doesn't quite convey how thorough it is. If I had a spell that would let me reach out to that address plate and touch it to feel the numbers, it still wouldn't work. The spell would still be linked to me, and that link would still make the concealment spell reach me."

"Okay," you say, thinking a bit. "So let's go back to how you felt that opposing force earlier. Would you be able to recognize that force affecting something else?"

"It's affecting everything on this ship. I don't see how that would help."

"Well, there's another ship nearby. Maybe they're getting pulled down, too."

Wiz looks thoughtful.

"Give me a moment. And please be quiet."

Another few minutes pass before he speaks.

"It's no good. The pirate ship's too far away for me to detect much. I did catch a glimpse of something magical on it, but our relative positions are shifting too much for me to really focus on whatever it is."

"Any chance that whatever you detected is the source of the downward pull?" Resk asks.

"Not directly. If it were then I'd run into the interference effect. There's a number of ways it could be indirectly involved, depending on what it is. But if you're thinking of taking more aggressive action, I'd advise against it. If it is related, disrupting it is as likely to have dangerous unintended effects as it is to solve the problem."

You're starting to feel in over your head. But then you wonder if there's another way to look at it. Maybe the answer isn't in the messy details of how magic works; maybe it's a matter of thinking about what the spells you know about are actually doing, and what someone might be trying to accomplish with them.

Seems worth a try, at least.