How do you deal with the class features of a PC that has been dominated?
Specifically, I am referring to animal companions, eidolons, and paladin mounts.
It looks like there was a thread about this some time ago that focused mostly on animal companions. I feel like eidolons change the nature of the question in some way. Allow me to explain.
If a druid is dominated, I would consider it pretty straightforward that he could also command his animal companion to attack whomever he would like. The animal companion pretty much answers to the druid.
If a paladin with a mount is dominated, I feel like the mount could be vaguely aware that something is up, but the paladin would probably be able to guide the mount to go wherever he needs to be. The mount, with his six intelligence, may be entitled to the Sense Motive check to recognize a dominated individual, but wouldn't necessarily be in a position to do anything about it. Generally speaking, I think the paladin could feasibly unleash his full mounted fury on the party. I feel like this wouldn't come up, but for the existence of the eidolon.
An eidolon is a distinct sentient outsider who manifests as an extension of a summoner's will. It is only a little smarter than a paladin mount (base INT 7). The difference I see is that it seems like an eidolon is far more capable of acting under his own power. It seems like there is the possibility that the eidolon is capable of recognizing that the summoner has turned against the party, and can make informed decisions from that.
The counter to this argument would be in the first line of my description of their relationship. There are no rules for how the summoner controls the eidolon - because the eidolon is a manifestation of the summoner's will. Perhaps there is no question. He does what the summoner wants. Or wait, is that corrupted by the meaning of dominate? What does the summoner, in fact, want?
Complicating this whole mess is the role-playing interaction. Whenever I play a character with a pet, I make sure that pet has a distinct personality. I encourage party members to interact with the dog or the serpent, and they each have their own relationships. That companion is almost as much of a PC as the PC is. So to me, it seems natural that a dominate cast on the PC is not automatically equivalent to a dominate on the pet.
But then, these things are class features. You wouldn't tell the rogue, "Well, you are dominated, but they don't get your sneak attack."
There's a lot more I can say about this, because I find it an interesting question. But I want to hear what you have to say first. I'll tell you more about the particular situation tomorrow.