[RPG] Can you use the Prodigy move with Magic Missile? Does that make it a cantrip

New answer for a renewed question. The old one is here

I'd say that a hidden move is quite against the grain of *World games'idea of moves. It robs the players of their agency in determining their characters' story.

And in your case, the intra-party conflict that may occur if the infiltrator is exposed seems to be more important than whether the infiltrator will be able to commit acts of sabotage and betrayal behind their backs. I'd base the move on that and add another move for the other party members to respond.

Infiltrator

You are an agent of your deity with a secret agenda. When you commit acts of sabotage and betrayal behind your comrades' backs, mark experience, and choose one comrade that doesn't already have it to receive the "Suspicious" move immediately.

Suspicious

You are suspicious of the infiltrator's weird behavior. When the Infiltrator commits acts of sabotage and betrayal behind your back, roll+INT.

• On a 10+, you have seen enough, but just need some more evidence. Replace this move with "Deeply Suspicious"
• On a 7-9, you noticed something unusual. Take +1 forward to your next "Suspicious" roll, but getting there wasn't easy. Choose one:
  • You had to get into trouble to get your information and come back with 1d8 damage.
  • Information is pricey. You had to spend 2d6x20 coin to find some clues.
  • Lies are everywhere. You wrongly implicate another comrade (The infiltrator will tell you who). You cannot aid or interfere with them until the next time you roll "suspicious"

Deeply suspicious

Replaces Suspicious

Same as "Suspicious" but add these to the list of possible outcomes.

• On a 12+ , you have enough evidence to expose and implicate the Infiltrator. Now everyone in the party knows better. You decide the fate of the traitor.
• On a 10-11, you collect a solid piece of evidence, slowly building a strong case. Give another comrade the "Suspicious" move if they don't already have it, or replace their "Suspicious" with "Deeply suspicious"

This is based on the assumption that the infiltrator is a well known and trusted member of the party in the beginning. The first act of the infiltrator is essentially free. His or her comrades suspect nothing in the beginning and they trust the infiltrator. But then it gets harder and riskier every time.

And yes, all this can and will eventually leave the fate of the infiltrator in the hands of another player. The question is, when?

Your first guess is right: go with the fiction.

First, a dozen hirelings without food for some days will get angry and non-compliant. They will probably run off or even turn against their employers. How should they believe that they will get their agreed-upon payment, if not even food is provided by the PCs?

Second, the PCs will get hungry, weak and eventually sick. Add in the corresponding debilities to show them the effects. Without rations they cannot Make Camp or Undertake A Perilous Journey. Travelling will be cumbersome and inconvenient.

If there's really no way for them to find food (it is hard to imagine that in most common environments there is absolutely nothing edible to be found), Show Them Signs Of An Approaching Threat: the few hirelings that are still with them start to turn mad with hunger. How long will it take until they start killing and eating each other?

However, with a good Spout Lore or Discern Realities, the PCs might be able to find something edible in the area. There's always some worms under a rock, some strange berries that the local animals avoid, the random vicious beast in its lair that no one dares to hunt...