How many Shapechanged Familiar Dragons can I have at once?

Question

As per this question, certain classes can indeed have multiple Animal Companions or Familiars able to share spells.

I want to know what the theoretical limit of this would be. A Druid19/Wiz1 would be able to supply 2, the Extra Familiar feat would be a third, while the Spell-Sharing Collar will let me have an extra 3 per original companion/familiar, for a total of 12 Dragons (4x Lvl6 Primal Form I, 4x Lvl7 Primal Form II, 1x Lvl8 Primal Form III, 3x Lvl9 Shapechange (At caster level 19, this would be 190 minutes for each Primal Dragon, and easily a full day for Shapechange.) This assumes that at theoretical level 20, the character would have accumulated a dragon-like horde so that money is not an object.

Am I missing anything that would let me increase this number at all?

Answer 1

PFSRD: Pack Lord Druid Archetype, Pack Bond class feature:

The share spells animal companion ability only applies to one animal companion at a time—the pack lord cannot use it to cast a one-target spell and have it affect all of her animal companions.

I've occasionally seen people read this and go "oh, only one of his companions can have share spells at a time." Reading more closely and paying attention to the example, it's actually "oh, each time he casts a single-target spell, he can only share it with one companion that casting." That means...

Drd(Pack Lord)19/Wiz1 supplies 19 animal companions and one familiar, Extra Familiar grants a 21st. If you can find enough creatures (note that the spell-sharing collar doesn't grant share spells, only allows a creature to chain-benefit from it) that qualify, you can add 63 more to that with 84 of the collars.

I find it likely you'll run out of spells to transform them long before you run out of pets. I ~think~, if I'm reading that collar right (I might not be, it's late), you can instead use 20 of the collars to bind your pets together in sets of four, and allow a single shapechange or primal form spell to affect four of them at a cast.

Regardless, I think you're looking at a minimum of nineteen animal companions and two familiars before counting magic items using the Pack Lord Druid Archetype.

Optimization note: Honestly, I'd just go Drd(Pack Lord) 20 and take twenty animal companions instead of bothering with the familiars, so I could change them all in five shapechanges (if you have the massive Wisdom needed for that one additional level 9 spell per day, or a pearl of power IX).