Allied/Friendly NPCs - Doom or Momentum?

A thought occurred to me as I was prepping for tomorrow’s game - if I have a friendly NPC traveling with the group for story reasons what do they use in terms of Momentum and Doom?

As an NPC do they add and subtract from the Doom pool like a regular NPC? It seems kind of counter-productive for an ally to generate Momentum which then adds to the GM’s Doom. Also seems strange that they would use Doom to help the PCs too as that is not in the spirit of what Doom is used for.

Or do they generate and use Momentum like a regular PC? Again this seems counter-productive as they can take Momentum meant for the players. Granted they can add to the pool as well but I hate the idea of an NPC taking a player resource away.

This NPC may be with the group for a little while so I want to make sure that they don’t take away from the PCs just because I want to add a layer to the story.

On p.102 in the Core Rulebook it is stated how to play ally and enemy NPCs:

​Unlike the player characters, non-player characters do not have the option of saving Momentum into a group pool.

  • Instead, any non-player character that concludes a task with Momentum left over can add a single point to the gamemaster’s Doom pool for each point of Momentum unspent.
  • Non-allied non-player characters can spend from the Doom pool just as player characters draw from the group Momentum pool.
  • Allied non-player characters can draw from the Momentum pool (if allowed by the players), but cannot add any earned Momentum to it. The Doom pool is described on page 269 and in Chapter Nine: Gamemastering.

Ah I must have missed that in there, thanks!