In Amber, there are various kinds of kinds of effects from Shapeshifting that can come into play... losing control of one's identity, consciousness, shape shifting cancer, or other effects.
My question is when do you usually bring these things into play? What does a player have to do for his shapeshifting to get outside of his control?
RPGPundit
Good question.
Personally, I've never had to do it. The few times there has been a shapeshifter in my games, they have used it to take combat forms, and that's about it.
Speaking of which, how much of a combat advantage is it, to have a combat form? How much stronger does it make you? How much faster? How much tougher?
At a base level, Shape Shifting is like changing your clothes: you put on armor, you grab a dagger, you blend into dark shadows, you slip into a scuba outfit, you rig a glider harness.
IOW, you react to environ with Shaping and gain some advantage. Some combat advantage goes with environ, but it is not always telling in combat unless the conflict is close already.
You are never faster by shaping, you might be slower, just as putting on heavy armor might slow you.
As for the first question: I vary this based on experience of the Player and trust banked with the GM. There are few players that really will gracefully let you throw those elements at them. I've had the pleasure of twisting that knife, but you really need to examine 'disconnecting' or disempowering a PC in such a fashion.