You cannot buy/sell the Brains themselves. When people 'sell' or 'auction off' the Brains they have, they get paid to buy specific gear or decor from the Event Shop to send to the person who paid for the Brains.
You cannot sell Familiars.
The Brains we got last year and didn't use remained stored in our accounts for this one, so it is reasonable to believe the same will happen this year.
Winter Month: 3 
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