Upon review, the Sanction should be 'Flaw', as Curse is general bad luck. Poisoning of the Boon is inappropriate, as it affects the hands, which ties into other rolls. The math still applies.
Fawkes looks at the floor as Sera flinches, clenching and un-clenching his hands. He shrugs at her compliment shyly,
"Um. I don't want you to use the Pledge to dismiss what happened. I think it helps others understand the importance of setting boundaries," he says. He doesn't mention how it will look to other Lost if a rumour went around that the mannequin tricked others into Pledges that allowed for great physical harm. "This is my way of making it up to you. If you want to award me something, that's up to you. I don't need the promise of the Wyrd to punish you if you don't. I'll be better at fighting as well, which will help my control."
He cocks his head, "I'm going off the assumption that you aren't used to this? You have choices how to seal it. We can swear on our True Names, invoke the name of our Keepers, or if you're religious, you can swear on who you answer to in the next life. All these have different consequences if you break the Pledge," he gives her a moment to ask questions and for the information to sink.
"The other way is using something from the environment as a symbol. That usually means the physical world will retaliate based on what we use. Like..." he looks around the hospital room and sees the orchid plant, "If I used a flower to represent the Spring Court, Courtiers would have the urge to come after me if I broke the agreement."
He hums to himself, "I'm going to swear on my Keeper. It means if I hurt you, They will come for me because I took a huge shit on Their honour," he chuckles darkly.