Mythgard's Noah is hosting a special Halloween stream on their official Twitch channel (dressed as a Rhino), and there's also a giveaway going on. You can find the codes in the spoiler bellow, but I highly recommend you stop by the stream. The codes are available while the stream is live (about 7 more hours from when this article goes up):

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HALLOWEENTRICK - 3 Core Set Packs

HALLOWEENTREAT - 3 Rings of Immortality packs

CANDY2020 - Plague Dr card trim

Reminder: If you can't make the stream, you can still earn the trim by entering the Discord costume contest by thend of November 1st.