Familiar: A swarm of, for example, bees. Or a nest of ants

If you were an SG allowing a player to have such a familiar, what would you apply as the rules governing it?

Personally I would rule the swarm size is capped at mass equal to the size modifier's maximum mass, and additional members of the swarm after that rapidly split off to join new swarms or nests.
This means you'd treat the familiar binding size as size 0 for that purpose, assuming it was a total size 0 swarm.

I'd adapt the rules for Aspects from magic beings, with the might pool being shared across the swarm, so many members of the swarm are might 0 because they aren't vital to the swarm, or don't need powers. The queen has the total might minus the might distributed to others and a power to redistribute the might across the swarm as needed and grant the other powers available to the various members of the swarm.

Personally, I would just have the Queen be treated as the familiar, with a Power allowing her to create a swarm that she can channel other Powers through. Swarms having individually important members sort of defeats the point of swarming, and if the whole swarm were treated as a Familiar then every member would become intelligent, likely causing conflicts with the hive mind mentality of a swarm.

IIRC, an Aspect of a Daimon has the full Might of the Daimon itself, since Aspecting is restricted through other means. So I wouldn't try to adapt those rules to the Swarm's Might.

Personally, if I were going to do this, I'd have you make a bond with the queen and have her command the workers. A bee in Mythic Europe is a distinct animal, not an interchangeable part of a greater swarm. (In other words, I agree with Lucky but not for the reasons they stated.)

I like the idea of the Queen, or King in the case of Bees, being the familiar and it controls the swarm.

The idea of insects having a group mind is more modern than medieval, so the King Bee (awesome size modifier :slight_smile: ) is probably more correct.

That said, taking the hive as a familiar wouldn't break anything: The binding total deserves +2 magnitudes for Group, I would think. That's a lot of bees.