The Blue Crown sent out an email to all their customers who placed an order between October 9th and October 31st. The email explains how they've had problems shipping Altruism decks due to the USPC's inaccurate delivery times. This was further compounded by the fact that their warehouse is in a storm-affected zone and still has no power.
As a thank-you for their customers' patience, they issued a single-use coupon code that's good until the end of the year for 10% off a future purchase.
If you received it, DO NOT DISTRIBUTE this code. It was a generous offer from TBC to keep their customers pleased and show their gratitude, and it should not be abused. If someone passed it to you, I'd hope you wouldn't abuse this, but at the very least don't redistribute it.