To be clear, if you try and fail to Deceive the Hag, then can you still attempt Intimidate her for both the power AND Mayrina? If you can't do this, then that's better than what I was thinking.
But I think there should still be some penalty for failing to deceive her. Maybe she no longer allows to choose Mayrina, or the power she gives you is slightly worse, or something. If you can roll a check for a better result, then failing that roll should have some consequence.
No no, the opposite. You only get to choose one speech check of your choice. If you fail, that's it, you no longer have a chance to obtain both Mayrina and the Power.
And I agree, would be interesting to have penalties for trying to gain more when beings of equal power are bargaining with us. Basically a high-risk high-reward situation.